从字符串数组中获取片段标题
Get fragment title from string array
所以我正在使用基于 ActionBarSherlock 的示例应用程序。我想从字符串数组中设置片段的标题，但是当我尝试在模拟器上 运行 它时，它给了我 NullPointerException 错误。
String[] title;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
String[] title = context.getResources().getStringArray(R.array.title);
private void selectItem(int position) {
setTitle(title[position]);
}
这只是我认为涉及的代码的一部分。
但这是我的全部代码。
package com.androidbegin.menuviewpagertutorial;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import com.actionbarsherlock.view.MenuItem;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.app.Fragment;
import android.content.Context;
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.support.v4.view.GravityCompat;
public class MainActivity extends SherlockFragmentActivity {
// Declare Variables
DrawerLayout mDrawerLayout;
ListView mDrawerList;
ActionBarDrawerToggle mDrawerToggle;
MenuListAdapter mMenuAdapter;
String[] title;
String[] subtitle;
int[] icon;
Fragment fragment1 = new Fragment1();
Fragment fragment2 = new Fragment2();
private CharSequence mDrawerTitle;
private CharSequence mTitle;
Context context;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Get the view from drawer_main.xml
setContentView(R.layout.drawer_main);
// Get the Title
mTitle = mDrawerTitle = getTitle();
// Generate title
String[] title = context.getResources().getStringArray(R.array.title);
// Generate subtitle
subtitle = new String[] { "Subtitle Fragment 1", "Subtitle Fragment 2" };
// Generate icon
icon = new int[] { R.drawable.action_about, R.drawable.action_settings };
// Locate DrawerLayout in drawer_main.xml
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
// Locate ListView in drawer_main.xml
mDrawerList = (ListView) findViewById(R.id.listview_drawer);
// Set a custom shadow that overlays the main content when the drawer
// opens
mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow,
GravityCompat.START);
// Pass string arrays to MenuListAdapter
mMenuAdapter = new MenuListAdapter(MainActivity.this, title, subtitle);
// Set the MenuListAdapter to the ListView
mDrawerList.setAdapter(mMenuAdapter);
// Capture listview menu item click
mDrawerList.setOnItemClickListener(new DrawerItemClickListener());
// Enable ActionBar app icon to behave as action to toggle nav drawer
getSupportActionBar().setHomeButtonEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
// ActionBarDrawerToggle ties together the the proper interactions
// between the sliding drawer and the action bar app icon
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer, R.string.drawer_open,
R.string.drawer_close) {
public void onDrawerClosed(View view) {
// TODO Auto-generated method stub
super.onDrawerClosed(view);
}
public void onDrawerOpened(View drawerView) {
// TODO Auto-generated method stub
// Set the title on the action when drawer open
getSupportActionBar().setTitle(mDrawerTitle);
super.onDrawerOpened(drawerView);
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
selectItem(0);
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == android.R.id.home) {
if (mDrawerLayout.isDrawerOpen(mDrawerList)) {
mDrawerLayout.closeDrawer(mDrawerList);
} else {
mDrawerLayout.openDrawer(mDrawerList);
}
}
return super.onOptionsItemSelected(item);
}
// ListView click listener in the navigation drawer
private class DrawerItemClickListener implements
ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
selectItem(position);
}
}
private void selectItem(int position) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
// Locate Position
switch (position) {
case 0:
ft.replace(R.id.content_frame, fragment1);
break;
case 1:
ft.replace(R.id.content_frame, fragment2);
break;
}
ft.commit();
mDrawerList.setItemChecked(position, true);
// Get the title followed by the position
setTitle(title[position]);
// Close drawer
mDrawerLayout.closeDrawer(mDrawerList);
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mDrawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Pass any configuration change to the drawer toggles
mDrawerToggle.onConfigurationChanged(newConfig);
}
@Override
public void setTitle(CharSequence title) {
mTitle = title;
getSupportActionBar().setTitle(mTitle);
}
@Override
public void onBackPressed() {
FragmentManager manager = getSupportFragmentManager();
if (manager.getBackStackEntryCount() > 0) {
// If there are back-stack entries, leave the FragmentActivity
// implementation take care of them.
manager.popBackStack();
} else {
// Otherwise, ask user if he wants to leave :)
super.onBackPressed();
}
}
}
Logcat:
02-19 13:42:31.357: E/AndroidRuntime(1877): FATAL EXCEPTION: main
02-19 13:42:31.357: E/AndroidRuntime(1877): Process: com.androidbegin.menuviewpagertutorial, PID: 1877
02-19 13:42:31.357: E/AndroidRuntime(1877): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.androidbegin.menuviewpagertutorial/com.androidbegin.menuviewpagertutorial.MainActivity}: java.lang.NullPointerException
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread.access0(ActivityThread.java:135)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.os.Handler.dispatchMessage(Handler.java:102)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.os.Looper.loop(Looper.java:136)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread.main(ActivityThread.java:5017)
02-19 13:42:31.357: E/AndroidRuntime(1877): at java.lang.reflect.Method.invokeNative(Native Method)
02-19 13:42:31.357: E/AndroidRuntime(1877): at java.lang.reflect.Method.invoke(Method.java:515)
02-19 13:42:31.357: E/AndroidRuntime(1877): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
02-19 13:42:31.357: E/AndroidRuntime(1877): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
02-19 13:42:31.357: E/AndroidRuntime(1877): at dalvik.system.NativeStart.main(Native Method)
02-19 13:42:31.357: E/AndroidRuntime(1877): Caused by: java.lang.NullPointerException
02-19 13:42:31.357: E/AndroidRuntime(1877): at com.androidbegin.menuviewpagertutorial.MainActivity.selectItem(MainActivity.java:143)
02-19 13:42:31.357: E/AndroidRuntime(1877): at com.androidbegin.menuviewpagertutorial.MainActivity.onCreate(MainActivity.java:99)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.Activity.performCreate(Activity.java:5231)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
02-19 13:42:31.357: E/AndroidRuntime(1877): ... 11 more
我不太明白mDrawerTitle和mTitle的用法，所以请帮助我理解并解决这个问题。
提前致谢。
上下文似乎没有被初始化，改变你的这一行
String[] title = context.getResources().getStringArray(R.array.title);
到
String[] title = getBaseContext().getResources().getStringArray(R.array.title);
所以我正在使用基于 ActionBarSherlock 的示例应用程序。我想从字符串数组中设置片段的标题，但是当我尝试在模拟器上 运行 它时，它给了我 NullPointerException 错误。
String[] title;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
String[] title = context.getResources().getStringArray(R.array.title);
private void selectItem(int position) {
setTitle(title[position]);
}
这只是我认为涉及的代码的一部分。 但这是我的全部代码。
package com.androidbegin.menuviewpagertutorial;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import com.actionbarsherlock.view.MenuItem;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.app.Fragment;
import android.content.Context;
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.support.v4.view.GravityCompat;
public class MainActivity extends SherlockFragmentActivity {
// Declare Variables
DrawerLayout mDrawerLayout;
ListView mDrawerList;
ActionBarDrawerToggle mDrawerToggle;
MenuListAdapter mMenuAdapter;
String[] title;
String[] subtitle;
int[] icon;
Fragment fragment1 = new Fragment1();
Fragment fragment2 = new Fragment2();
private CharSequence mDrawerTitle;
private CharSequence mTitle;
Context context;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Get the view from drawer_main.xml
setContentView(R.layout.drawer_main);
// Get the Title
mTitle = mDrawerTitle = getTitle();
// Generate title
String[] title = context.getResources().getStringArray(R.array.title);
// Generate subtitle
subtitle = new String[] { "Subtitle Fragment 1", "Subtitle Fragment 2" };
// Generate icon
icon = new int[] { R.drawable.action_about, R.drawable.action_settings };
// Locate DrawerLayout in drawer_main.xml
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
// Locate ListView in drawer_main.xml
mDrawerList = (ListView) findViewById(R.id.listview_drawer);
// Set a custom shadow that overlays the main content when the drawer
// opens
mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow,
GravityCompat.START);
// Pass string arrays to MenuListAdapter
mMenuAdapter = new MenuListAdapter(MainActivity.this, title, subtitle);
// Set the MenuListAdapter to the ListView
mDrawerList.setAdapter(mMenuAdapter);
// Capture listview menu item click
mDrawerList.setOnItemClickListener(new DrawerItemClickListener());
// Enable ActionBar app icon to behave as action to toggle nav drawer
getSupportActionBar().setHomeButtonEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
// ActionBarDrawerToggle ties together the the proper interactions
// between the sliding drawer and the action bar app icon
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
R.drawable.ic_drawer, R.string.drawer_open,
R.string.drawer_close) {
public void onDrawerClosed(View view) {
// TODO Auto-generated method stub
super.onDrawerClosed(view);
}
public void onDrawerOpened(View drawerView) {
// TODO Auto-generated method stub
// Set the title on the action when drawer open
getSupportActionBar().setTitle(mDrawerTitle);
super.onDrawerOpened(drawerView);
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
selectItem(0);
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == android.R.id.home) {
if (mDrawerLayout.isDrawerOpen(mDrawerList)) {
mDrawerLayout.closeDrawer(mDrawerList);
} else {
mDrawerLayout.openDrawer(mDrawerList);
}
}
return super.onOptionsItemSelected(item);
}
// ListView click listener in the navigation drawer
private class DrawerItemClickListener implements
ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
selectItem(position);
}
}
private void selectItem(int position) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
// Locate Position
switch (position) {
case 0:
ft.replace(R.id.content_frame, fragment1);
break;
case 1:
ft.replace(R.id.content_frame, fragment2);
break;
}
ft.commit();
mDrawerList.setItemChecked(position, true);
// Get the title followed by the position
setTitle(title[position]);
// Close drawer
mDrawerLayout.closeDrawer(mDrawerList);
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mDrawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Pass any configuration change to the drawer toggles
mDrawerToggle.onConfigurationChanged(newConfig);
}
@Override
public void setTitle(CharSequence title) {
mTitle = title;
getSupportActionBar().setTitle(mTitle);
}
@Override
public void onBackPressed() {
FragmentManager manager = getSupportFragmentManager();
if (manager.getBackStackEntryCount() > 0) {
// If there are back-stack entries, leave the FragmentActivity
// implementation take care of them.
manager.popBackStack();
} else {
// Otherwise, ask user if he wants to leave :)
super.onBackPressed();
}
}
}
Logcat:
02-19 13:42:31.357: E/AndroidRuntime(1877): FATAL EXCEPTION: main
02-19 13:42:31.357: E/AndroidRuntime(1877): Process: com.androidbegin.menuviewpagertutorial, PID: 1877
02-19 13:42:31.357: E/AndroidRuntime(1877): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.androidbegin.menuviewpagertutorial/com.androidbegin.menuviewpagertutorial.MainActivity}: java.lang.NullPointerException
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread.access0(ActivityThread.java:135)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.os.Handler.dispatchMessage(Handler.java:102)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.os.Looper.loop(Looper.java:136)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread.main(ActivityThread.java:5017)
02-19 13:42:31.357: E/AndroidRuntime(1877): at java.lang.reflect.Method.invokeNative(Native Method)
02-19 13:42:31.357: E/AndroidRuntime(1877): at java.lang.reflect.Method.invoke(Method.java:515)
02-19 13:42:31.357: E/AndroidRuntime(1877): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
02-19 13:42:31.357: E/AndroidRuntime(1877): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
02-19 13:42:31.357: E/AndroidRuntime(1877): at dalvik.system.NativeStart.main(Native Method)
02-19 13:42:31.357: E/AndroidRuntime(1877): Caused by: java.lang.NullPointerException
02-19 13:42:31.357: E/AndroidRuntime(1877): at com.androidbegin.menuviewpagertutorial.MainActivity.selectItem(MainActivity.java:143)
02-19 13:42:31.357: E/AndroidRuntime(1877): at com.androidbegin.menuviewpagertutorial.MainActivity.onCreate(MainActivity.java:99)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.Activity.performCreate(Activity.java:5231)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
02-19 13:42:31.357: E/AndroidRuntime(1877): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
02-19 13:42:31.357: E/AndroidRuntime(1877): ... 11 more
我不太明白mDrawerTitle和mTitle的用法，所以请帮助我理解并解决这个问题。
提前致谢。
上下文似乎没有被初始化，改变你的这一行
String[] title = context.getResources().getStringArray(R.array.title);
到
String[] title = getBaseContext().getResources().getStringArray(R.array.title);