具有多个活动的导航抽屉。 - 空指针异常
Navigation Drawer with Multiple activities. - NullPointerException
我正在通过 Android Studio 开发我的移动应用程序。我的应用程序的启动器 activity 是 SplashScreen。 SplashScreen 和 Intent 导航到我的 HomeActivity。我尝试了 this 博客中的代码，这样我就可以有一个导航抽屉，但在活动之间而不是片段之间。
在Splashscreen和HomeActivity活动中，我不想要这个抽屉。在 HomeActivity 中有一个按钮 (signin)。当您按下它时，您通常会导航到 SearchActivity，这是我想要放置导航抽屉的第一页。
在上面的示例中，启动器 activity 是 BaseActivity。因为我不想 BaseActivity 成为我的启动器 activity，正如我所描述的，我在单击 HomeActivity 内的 signin 按钮后导航到 BaseActivity .
我的HomeActivity.java:
import android.content.Intent;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ViewAnimator;
import common.activities.SampleActivityBase;
import common.logger.Log;
import common.logger.LogFragment;
import common.logger.LogWrapper;
import common.logger.MessageOnlyLogFilter;
public class HomeActivity extends SampleActivityBase {
public static final String TAG = "HomeActivity";
// Whether the Log Fragment is currently shown
private boolean mLogShown;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final ImageButton send = (ImageButton)findViewById(R.id.signin);
send.setOnClickListener(new View.OnClickListener()
{
public void onClick(View view)
{
Intent intent = new Intent(HomeActivity.this, BaseActivity.class);
startActivity(intent);
finish();
}
});
if (savedInstanceState == null) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
SlidingTabsColorsFragment fragment = new SlidingTabsColorsFragment();
transaction.replace(R.id.sample_content_fragment, fragment);
transaction.commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
MenuItem logToggle = menu.findItem(R.id.menu_toggle_log);
logToggle.setVisible(findViewById(R.id.sample_output) instanceof ViewAnimator);
logToggle.setTitle(mLogShown ? "hide" : "show");
return super.onPrepareOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// switch(item.getItemId()) {
// case R.id.menu_toggle_log:
// mLogShown = !mLogShown;
// ViewAnimator output = (ViewAnimator) findViewById(R.id.sample_output);
// if (mLogShown) {
// //output.setDisplayedChild(1);
// } else {
// //output.setDisplayedChild(0);
// }
// supportInvalidateOptionsMenu();
// return true;
// }
return super.onOptionsItemSelected(item);
}
/** Create a chain of targets that will receive log data */
@Override
public void initializeLogging() {
// Wraps Android's native log framework.
LogWrapper logWrapper = new LogWrapper();
// Using Log, front-end to the logging chain, emulates android.util.log method signatures.
Log.setLogNode(logWrapper);
// Filter strips out everything except the message text.
MessageOnlyLogFilter msgFilter = new MessageOnlyLogFilter();
logWrapper.setNext(msgFilter);
// On screen logging via a fragment with a TextView.
// LogFragment logFragment = (LogFragment) getSupportFragmentManager()
// .findFragmentById(R.id.log_fragment);
// msgFilter.setNext(logFragment.getLogView());
//
// Log.i(TAG, "Ready");
}
}
我的基础活动：
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.FrameLayout;
import android.widget.ListView;
import android.widget.Toast;
/**
* @author dipenp
*
* This activity will add Navigation Drawer for our application and all the code related to navigation drawer.
* We are going to extend all our other activites from this BaseActivity so that every activity will have Navigation Drawer in it.
* This activity layout contain one frame layout in which we will add our child activity layout.
*/
public class BaseActivity extends Activity {
/**
* Frame layout: Which is going to be used as parent layout for child activity layout.
* This layout is protected so that child activity can access this
* */
protected FrameLayout frameLayout;
/**
* ListView to add navigation drawer item in it.
* We have made it protected to access it in child class. We will just use it in child class to make item selected according to activity opened.
*/
protected ListView mDrawerList;
/**
* List item array for navigation drawer items.
* */
protected String[] listArray = { "Item 1", "Item 2", "Item 3", "Item 4", "Item 5" };
/**
* Static variable for selected item position. Which can be used in child activity to know which item is selected from the list.
* */
protected static int position;
/**
* This flag is used just to check that launcher activity is called first time
* so that we can open appropriate Activity on launch and make list item position selected accordingly.
* */
private static boolean isLaunch = true;
/**
* Base layout node of this Activity.
* */
private DrawerLayout mDrawerLayout;
/**
* Drawer listner class for drawer open, close etc.
*/
private ActionBarDrawerToggle actionBarDrawerToggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.navigation_drawer_base_layout);
frameLayout = (FrameLayout)findViewById(R.id.content_frame);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
// set a custom shadow that overlays the main content when the drawer opens
//mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
// set up the drawer's list view with items and click listener
mDrawerList.setAdapter(new ArrayAdapter<String>(this, R.layout.drawer_list_item, listArray));
mDrawerList.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
openActivity(position);
}
});
// enable ActionBar app icon to behave as action to toggle nav drawer
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
// ActionBarDrawerToggle ties together the the proper interactions between the sliding drawer and the action bar app icon
actionBarDrawerToggle = new ActionBarDrawerToggle(
this, /* host Activity */
mDrawerLayout, /* DrawerLayout object */
R.drawable.ic_launcher, /* nav drawer image to replace 'Up' caret */
R.string.drawer_open, /* "open drawer" description for accessibility */
R.string.drawer_close) /* "close drawer" description for accessibility */
{
@Override
public void onDrawerClosed(View drawerView) {
getActionBar().setTitle(listArray[position]);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
super.onDrawerClosed(drawerView);
}
@Override
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(getString(R.string.app_name));
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
super.onDrawerOpened(drawerView);
}
@Override
public void onDrawerSlide(View drawerView, float slideOffset) {
super.onDrawerSlide(drawerView, slideOffset);
}
@Override
public void onDrawerStateChanged(int newState) {
super.onDrawerStateChanged(newState);
}
};
mDrawerLayout.setDrawerListener(actionBarDrawerToggle);
/**
* As we are calling BaseActivity from manifest file and this base activity is intended just to add navigation drawer in our app.
* We have to open some activity with layout on launch. So we are checking if this BaseActivity is called first time then we are opening our first activity.
* */
if(isLaunch){
/**
*Setting this flag false so that next time it will not open our first activity.
*We have to use this flag because we are using this BaseActivity as parent activity to our other activity.
*In this case this base activity will always be call when any child activity will launch.
*/
isLaunch = false;
openActivity(0);
}
}
/**
* @param position
*
* Launching activity when any list item is clicked.
*/
protected void openActivity(int position) {
/**
* We can set title & itemChecked here but as this BaseActivity is parent for other activity,
* So whenever any activity is going to launch this BaseActivity is also going to be called and
* it will reset this value because of initialization in onCreate method.
* So that we are setting this in child activity.
*/
// mDrawerList.setItemChecked(position, true);
// setTitle(listArray[position]);
mDrawerLayout.closeDrawer(mDrawerList);
BaseActivity.position = position; //Setting currently selected position in this field so that it will be available in our child activities.
switch (position) {
case 0:
startActivity(new Intent(this, SearchActivity.class));
break;
case 1:
startActivity(new Intent(this, SearchActivity.class));
break;
case 2:
startActivity(new Intent(this, SearchActivity.class));
break;
case 3:
startActivity(new Intent(this, SearchActivity.class));
break;
case 4:
startActivity(new Intent(this, SearchActivity.class));
break;
default:
break;
}
Toast.makeText(this, "Selected Item Position::"+position, Toast.LENGTH_LONG).show();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// The action bar home/up action should open or close the drawer.
// ActionBarDrawerToggle will take care of this.
if (actionBarDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
switch (item.getItemId()) {
case R.id.action_settings:
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/* Called whenever we call invalidateOptionsMenu() */
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the nav drawer is open, hide action items related to the content view
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
/* We can override onBackPressed method to toggle navigation drawer*/
@Override
public void onBackPressed() {
if(mDrawerLayout.isDrawerOpen(mDrawerList)){
mDrawerLayout.closeDrawer(mDrawerList);
}else {
mDrawerLayout.openDrawer(mDrawerList);
}
}
}
我的搜索活动：
import android.content.Context;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.os.Bundle;
import android.widget.ImageView;
public class SearchActivity extends BaseActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/**
* We will not use setContentView in this activty
* Rather than we will use layout inflater to add view in FrameLayout of our base activity layout*/
/**
* Adding our layout to parent class frame layout.
*/
getLayoutInflater().inflate(R.layout.activity_search, frameLayout);
/**
* Setting title and itemChecked
*/
mDrawerList.setItemChecked(position, true);
setTitle(listArray[position]);
//((ImageView)findViewById(R.id.image_view)).setBackgroundResource(R.drawable.image1);
}
}
drawer_list_item.xml:
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:textColor="#fff"/>
还有我的navigation_drawer_layout.xml：
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<FrameLayout
android:id="@+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<ListView
android:id="@+id/left_drawer"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:background="#111"
android:choiceMode="singleChoice"
android:divider="@android:color/transparent"
android:dividerHeight="0dp" />
</android.support.v4.widget.DrawerLayout>
这就是与我正在尝试做的事情相关的全部代码。
当我按下 HomeActivity 中的 signin 按钮时，出现以下错误：
01-06 13:39:45.563 17197-17197/guide_me_for_all.guide_me_for_all E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: guide_me_for_all.guide_me_for_all, PID: 17197
java.lang.RuntimeException: Unable to start activity ComponentInfo{guide_me_for_all.guide_me_for_all/guide_me_for_all.guide_me_for_all.BaseActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2212)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
at android.app.ActivityThread.access0(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5146)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at guide_me_for_all.guide_me_for_all.BaseActivity.onCreate(BaseActivity.java:92)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
at android.app.ActivityThread.access0(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5146)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
at dalvik.system.NativeStart.main(Native Method)
你能打电话给
setContentView(R.layout. navigation_drawer_layout);
而不是
setContentView(R.layout.navigation_drawer_base_layout);
在 BaseActivity?
这个错误一般发生在访问findViewById出错的时候。只需注释掉 mDrawerList.setItemChecked(position, true); 即可检查是否是问题所在。
在基本活动中像这样覆盖 setContentView()。
@Override
public void setContentView(int layoutResID) {
mDrawerLayout = (DrawerLayout) getLayoutInflater().inflate(
R.layout.activity_base, null);
mFrameLayout = (FrameLayout) mDrawerLayout
.findViewById(R.id.frame_container);
mDrawerList = (ExpandableListView) mDrawerLayout
.findViewById(R.id.left_drawer);
getLayoutInflater().inflate(layoutResID, mFrameLayout, true);
super.setContentView(mDrawerLayout);
//Your custom code
}
您可能想尝试以下方法：
public class BaseActivity extends Activity {
protected FrameLayout frameLayout;
protected ListView mDrawerList;
protected String[] listArray = { "Item 1", "Item 2", "Item 3", "Item 4", "Item 5" };
private static boolean isLaunch = true;
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle actionBarDrawerToggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.navigation_drawer_base_layout);
frameLayout = (FrameLayout)findViewById(R.id.content_frame);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
//mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
mDrawerList.setAdapter(new ArrayAdapter<String>(this, R.layout.drawer_list_item, listArray));
mDrawerList.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
openActivity(position);
getSupportActionBar().setTitle(listArray[position]);
}
});
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
actionBarDrawerToggle = new ActionBarDrawerToggle(
this, /* host Activity */
mDrawerLayout, /* DrawerLayout object */
R.drawable.ic_launcher, /* nav drawer image to replace 'Up' caret */
R.string.drawer_open, /* "open drawer" description for accessibility */
R.string.drawer_close) /* "close drawer" description for accessibility */
{
@Override
public void onDrawerClosed(View drawerView) {
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
super.onDrawerClosed(drawerView);
}
@Override
public void onDrawerOpened(View drawerView) {
//use the support library in App Combat
getSupportActionBar().setTitle(getString(R.string.app_name));
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
super.onDrawerOpened(drawerView);
}
@Override
public void onDrawerSlide(View drawerView, float slideOffset) {
super.onDrawerSlide(drawerView, slideOffset);
}
@Override
public void onDrawerStateChanged(int newState) {
super.onDrawerStateChanged(newState);
}
};
mDrawerLayout.setDrawerListener(actionBarDrawerToggle);
//in the line below you will always get the Selected position 0 because your isLaunch = true, so it will always give you this toast. If you think its unessecary remove it.
if(isLaunch){
isLaunch = false;
openActivity(0);
}
}
由于 Navigation Drawer 与 Fragments 一起使用，请尝试这种方法：
protected Fragment openActivity(int position) {
mDrawerLayout.closeDrawer(mDrawerList);
Fragment fragment = null;
switch (position) {
case 0:{
fragment = new SearchActivity();
break;
}
case 1:{
fragment = new A();
break;
}
case 2:{
fragment = new B();
break;
}
case 3: {
fragment = new C();
break;
}
case 4:{
fragment = new D();
break;
}
}
FragmentManager fm = getSupportFragmentManager();
fm.beginTransaction().replace(R.id.content_frame, fragment).commit();
return fragment;
}
这样使用onOptionsItemSelected方法：
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (actionBarDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
return super.onOptionsItemSelected(item);
}
onBackPressed 方法如下：
删除 else 语句，因为你不想按下后退按钮并打开抽屉
/* We can override onBackPressed method to toggle navigation drawer*/
@Override
public void onBackPressed() {
if(mDrawerLayout.isDrawerOpen(mDrawerList)){
mDrawerLayout.closeDrawer(mDrawerList);
}
}
同时将您的 SearchActivity 修改为一个片段，因为您希望在抽屉打开时成为第一个片段：
public class SearchActivity extends Fragment{
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View convertView = null;
if(convertView == null){
convertView= getLayoutInflater(savedInstanceState).inflate(R.layout.activity_search, container, false);
}
return convertView;
}
}
希望对您有所帮助！！！
我正在通过 Android Studio 开发我的移动应用程序。我的应用程序的启动器 activity 是 SplashScreen。 SplashScreen 和 Intent 导航到我的 HomeActivity。我尝试了 this 博客中的代码，这样我就可以有一个导航抽屉，但在活动之间而不是片段之间。
在Splashscreen和HomeActivity活动中，我不想要这个抽屉。在 HomeActivity 中有一个按钮 (signin)。当您按下它时，您通常会导航到 SearchActivity，这是我想要放置导航抽屉的第一页。
在上面的示例中，启动器 activity 是 BaseActivity。因为我不想 BaseActivity 成为我的启动器 activity，正如我所描述的，我在单击 HomeActivity 内的 signin 按钮后导航到 BaseActivity .
我的HomeActivity.java:
import android.content.Intent;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ViewAnimator;
import common.activities.SampleActivityBase;
import common.logger.Log;
import common.logger.LogFragment;
import common.logger.LogWrapper;
import common.logger.MessageOnlyLogFilter;
public class HomeActivity extends SampleActivityBase {
public static final String TAG = "HomeActivity";
// Whether the Log Fragment is currently shown
private boolean mLogShown;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final ImageButton send = (ImageButton)findViewById(R.id.signin);
send.setOnClickListener(new View.OnClickListener()
{
public void onClick(View view)
{
Intent intent = new Intent(HomeActivity.this, BaseActivity.class);
startActivity(intent);
finish();
}
});
if (savedInstanceState == null) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
SlidingTabsColorsFragment fragment = new SlidingTabsColorsFragment();
transaction.replace(R.id.sample_content_fragment, fragment);
transaction.commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
MenuItem logToggle = menu.findItem(R.id.menu_toggle_log);
logToggle.setVisible(findViewById(R.id.sample_output) instanceof ViewAnimator);
logToggle.setTitle(mLogShown ? "hide" : "show");
return super.onPrepareOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// switch(item.getItemId()) {
// case R.id.menu_toggle_log:
// mLogShown = !mLogShown;
// ViewAnimator output = (ViewAnimator) findViewById(R.id.sample_output);
// if (mLogShown) {
// //output.setDisplayedChild(1);
// } else {
// //output.setDisplayedChild(0);
// }
// supportInvalidateOptionsMenu();
// return true;
// }
return super.onOptionsItemSelected(item);
}
/** Create a chain of targets that will receive log data */
@Override
public void initializeLogging() {
// Wraps Android's native log framework.
LogWrapper logWrapper = new LogWrapper();
// Using Log, front-end to the logging chain, emulates android.util.log method signatures.
Log.setLogNode(logWrapper);
// Filter strips out everything except the message text.
MessageOnlyLogFilter msgFilter = new MessageOnlyLogFilter();
logWrapper.setNext(msgFilter);
// On screen logging via a fragment with a TextView.
// LogFragment logFragment = (LogFragment) getSupportFragmentManager()
// .findFragmentById(R.id.log_fragment);
// msgFilter.setNext(logFragment.getLogView());
//
// Log.i(TAG, "Ready");
}
}
我的基础活动：
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.FrameLayout;
import android.widget.ListView;
import android.widget.Toast;
/**
* @author dipenp
*
* This activity will add Navigation Drawer for our application and all the code related to navigation drawer.
* We are going to extend all our other activites from this BaseActivity so that every activity will have Navigation Drawer in it.
* This activity layout contain one frame layout in which we will add our child activity layout.
*/
public class BaseActivity extends Activity {
/**
* Frame layout: Which is going to be used as parent layout for child activity layout.
* This layout is protected so that child activity can access this
* */
protected FrameLayout frameLayout;
/**
* ListView to add navigation drawer item in it.
* We have made it protected to access it in child class. We will just use it in child class to make item selected according to activity opened.
*/
protected ListView mDrawerList;
/**
* List item array for navigation drawer items.
* */
protected String[] listArray = { "Item 1", "Item 2", "Item 3", "Item 4", "Item 5" };
/**
* Static variable for selected item position. Which can be used in child activity to know which item is selected from the list.
* */
protected static int position;
/**
* This flag is used just to check that launcher activity is called first time
* so that we can open appropriate Activity on launch and make list item position selected accordingly.
* */
private static boolean isLaunch = true;
/**
* Base layout node of this Activity.
* */
private DrawerLayout mDrawerLayout;
/**
* Drawer listner class for drawer open, close etc.
*/
private ActionBarDrawerToggle actionBarDrawerToggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.navigation_drawer_base_layout);
frameLayout = (FrameLayout)findViewById(R.id.content_frame);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
// set a custom shadow that overlays the main content when the drawer opens
//mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
// set up the drawer's list view with items and click listener
mDrawerList.setAdapter(new ArrayAdapter<String>(this, R.layout.drawer_list_item, listArray));
mDrawerList.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
openActivity(position);
}
});
// enable ActionBar app icon to behave as action to toggle nav drawer
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
// ActionBarDrawerToggle ties together the the proper interactions between the sliding drawer and the action bar app icon
actionBarDrawerToggle = new ActionBarDrawerToggle(
this, /* host Activity */
mDrawerLayout, /* DrawerLayout object */
R.drawable.ic_launcher, /* nav drawer image to replace 'Up' caret */
R.string.drawer_open, /* "open drawer" description for accessibility */
R.string.drawer_close) /* "close drawer" description for accessibility */
{
@Override
public void onDrawerClosed(View drawerView) {
getActionBar().setTitle(listArray[position]);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
super.onDrawerClosed(drawerView);
}
@Override
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(getString(R.string.app_name));
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
super.onDrawerOpened(drawerView);
}
@Override
public void onDrawerSlide(View drawerView, float slideOffset) {
super.onDrawerSlide(drawerView, slideOffset);
}
@Override
public void onDrawerStateChanged(int newState) {
super.onDrawerStateChanged(newState);
}
};
mDrawerLayout.setDrawerListener(actionBarDrawerToggle);
/**
* As we are calling BaseActivity from manifest file and this base activity is intended just to add navigation drawer in our app.
* We have to open some activity with layout on launch. So we are checking if this BaseActivity is called first time then we are opening our first activity.
* */
if(isLaunch){
/**
*Setting this flag false so that next time it will not open our first activity.
*We have to use this flag because we are using this BaseActivity as parent activity to our other activity.
*In this case this base activity will always be call when any child activity will launch.
*/
isLaunch = false;
openActivity(0);
}
}
/**
* @param position
*
* Launching activity when any list item is clicked.
*/
protected void openActivity(int position) {
/**
* We can set title & itemChecked here but as this BaseActivity is parent for other activity,
* So whenever any activity is going to launch this BaseActivity is also going to be called and
* it will reset this value because of initialization in onCreate method.
* So that we are setting this in child activity.
*/
// mDrawerList.setItemChecked(position, true);
// setTitle(listArray[position]);
mDrawerLayout.closeDrawer(mDrawerList);
BaseActivity.position = position; //Setting currently selected position in this field so that it will be available in our child activities.
switch (position) {
case 0:
startActivity(new Intent(this, SearchActivity.class));
break;
case 1:
startActivity(new Intent(this, SearchActivity.class));
break;
case 2:
startActivity(new Intent(this, SearchActivity.class));
break;
case 3:
startActivity(new Intent(this, SearchActivity.class));
break;
case 4:
startActivity(new Intent(this, SearchActivity.class));
break;
default:
break;
}
Toast.makeText(this, "Selected Item Position::"+position, Toast.LENGTH_LONG).show();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// The action bar home/up action should open or close the drawer.
// ActionBarDrawerToggle will take care of this.
if (actionBarDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
switch (item.getItemId()) {
case R.id.action_settings:
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/* Called whenever we call invalidateOptionsMenu() */
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the nav drawer is open, hide action items related to the content view
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
/* We can override onBackPressed method to toggle navigation drawer*/
@Override
public void onBackPressed() {
if(mDrawerLayout.isDrawerOpen(mDrawerList)){
mDrawerLayout.closeDrawer(mDrawerList);
}else {
mDrawerLayout.openDrawer(mDrawerList);
}
}
}
我的搜索活动：
import android.content.Context;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.os.Bundle;
import android.widget.ImageView;
public class SearchActivity extends BaseActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/**
* We will not use setContentView in this activty
* Rather than we will use layout inflater to add view in FrameLayout of our base activity layout*/
/**
* Adding our layout to parent class frame layout.
*/
getLayoutInflater().inflate(R.layout.activity_search, frameLayout);
/**
* Setting title and itemChecked
*/
mDrawerList.setItemChecked(position, true);
setTitle(listArray[position]);
//((ImageView)findViewById(R.id.image_view)).setBackgroundResource(R.drawable.image1);
}
}
drawer_list_item.xml:
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:textColor="#fff"/>
还有我的navigation_drawer_layout.xml：
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<FrameLayout
android:id="@+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<ListView
android:id="@+id/left_drawer"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:background="#111"
android:choiceMode="singleChoice"
android:divider="@android:color/transparent"
android:dividerHeight="0dp" />
</android.support.v4.widget.DrawerLayout>
这就是与我正在尝试做的事情相关的全部代码。
当我按下 HomeActivity 中的 signin 按钮时，出现以下错误：
01-06 13:39:45.563 17197-17197/guide_me_for_all.guide_me_for_all E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: guide_me_for_all.guide_me_for_all, PID: 17197
java.lang.RuntimeException: Unable to start activity ComponentInfo{guide_me_for_all.guide_me_for_all/guide_me_for_all.guide_me_for_all.BaseActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2212)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
at android.app.ActivityThread.access0(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5146)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at guide_me_for_all.guide_me_for_all.BaseActivity.onCreate(BaseActivity.java:92)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
at android.app.ActivityThread.access0(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5146)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
at dalvik.system.NativeStart.main(Native Method)
你能打电话给
setContentView(R.layout. navigation_drawer_layout);
而不是
setContentView(R.layout.navigation_drawer_base_layout);
在 BaseActivity?
这个错误一般发生在访问findViewById出错的时候。只需注释掉 mDrawerList.setItemChecked(position, true); 即可检查是否是问题所在。
在基本活动中像这样覆盖 setContentView()。
@Override
public void setContentView(int layoutResID) {
mDrawerLayout = (DrawerLayout) getLayoutInflater().inflate(
R.layout.activity_base, null);
mFrameLayout = (FrameLayout) mDrawerLayout
.findViewById(R.id.frame_container);
mDrawerList = (ExpandableListView) mDrawerLayout
.findViewById(R.id.left_drawer);
getLayoutInflater().inflate(layoutResID, mFrameLayout, true);
super.setContentView(mDrawerLayout);
//Your custom code
}
您可能想尝试以下方法：
public class BaseActivity extends Activity {
protected FrameLayout frameLayout;
protected ListView mDrawerList;
protected String[] listArray = { "Item 1", "Item 2", "Item 3", "Item 4", "Item 5" };
private static boolean isLaunch = true;
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle actionBarDrawerToggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.navigation_drawer_base_layout);
frameLayout = (FrameLayout)findViewById(R.id.content_frame);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
//mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
mDrawerList.setAdapter(new ArrayAdapter<String>(this, R.layout.drawer_list_item, listArray));
mDrawerList.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
openActivity(position);
getSupportActionBar().setTitle(listArray[position]);
}
});
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
actionBarDrawerToggle = new ActionBarDrawerToggle(
this, /* host Activity */
mDrawerLayout, /* DrawerLayout object */
R.drawable.ic_launcher, /* nav drawer image to replace 'Up' caret */
R.string.drawer_open, /* "open drawer" description for accessibility */
R.string.drawer_close) /* "close drawer" description for accessibility */
{
@Override
public void onDrawerClosed(View drawerView) {
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
super.onDrawerClosed(drawerView);
}
@Override
public void onDrawerOpened(View drawerView) {
//use the support library in App Combat
getSupportActionBar().setTitle(getString(R.string.app_name));
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
super.onDrawerOpened(drawerView);
}
@Override
public void onDrawerSlide(View drawerView, float slideOffset) {
super.onDrawerSlide(drawerView, slideOffset);
}
@Override
public void onDrawerStateChanged(int newState) {
super.onDrawerStateChanged(newState);
}
};
mDrawerLayout.setDrawerListener(actionBarDrawerToggle);
//in the line below you will always get the Selected position 0 because your isLaunch = true, so it will always give you this toast. If you think its unessecary remove it.
if(isLaunch){
isLaunch = false;
openActivity(0);
}
}
由于 Navigation Drawer 与 Fragments 一起使用，请尝试这种方法：
protected Fragment openActivity(int position) {
mDrawerLayout.closeDrawer(mDrawerList);
Fragment fragment = null;
switch (position) {
case 0:{
fragment = new SearchActivity();
break;
}
case 1:{
fragment = new A();
break;
}
case 2:{
fragment = new B();
break;
}
case 3: {
fragment = new C();
break;
}
case 4:{
fragment = new D();
break;
}
}
FragmentManager fm = getSupportFragmentManager();
fm.beginTransaction().replace(R.id.content_frame, fragment).commit();
return fragment;
}
这样使用onOptionsItemSelected方法：
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (actionBarDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
return super.onOptionsItemSelected(item);
}
onBackPressed 方法如下：
删除 else 语句，因为你不想按下后退按钮并打开抽屉
/* We can override onBackPressed method to toggle navigation drawer*/
@Override
public void onBackPressed() {
if(mDrawerLayout.isDrawerOpen(mDrawerList)){
mDrawerLayout.closeDrawer(mDrawerList);
}
}
同时将您的 SearchActivity 修改为一个片段，因为您希望在抽屉打开时成为第一个片段：
public class SearchActivity extends Fragment{
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View convertView = null;
if(convertView == null){
convertView= getLayoutInflater(savedInstanceState).inflate(R.layout.activity_search, container, false);
}
return convertView;
}
}
希望对您有所帮助！！！