尝试通过单击按钮更改 textView 中的文本大小时应用程序崩溃

Question

在我的一个 Activity 中，我有一个带有文本选项的菜单选项，当用户单击它时，它会重定向到另一个布局，其中我保留了两个按钮，一个是 加号按钮 另一个是 减号按钮

当用户单击该按钮时我想更改 BackStack 的 TextView 文本大小Activity

下面是我的代码当我点击 MenuOPtion 时，应用程序崩溃了，它在 Logcat

中报告 NullPointerException

我的详细信息Activity

@Override
    protected void onCreate(Bundle savedInstanceState) {


        super.onCreate(savedInstanceState);
        setContentView(R.layout.detail_activity);

 detailtext= (TextView) findViewById(R.id.detail);
 dbHelper = new SqlLiteDbHelper(this);
        try {
            dbHelper.openDataBase();
        } catch (SQLException e) {
            e.printStackTrace();
        }

        sqLiteDatabase = dbHelper.getReadableDatabase();
        cursor=dbHelper.getdetails(sqLiteDatabase, selectedData);

        if(cursor.moveToFirst())
        {

            detailtext.setText(cursor.getString(0));
        }

@Override
    public boolean onOptionsItemSelected(MenuItem item) {
 int id = item.getItemId();
 if (id==R.id.text_option)
        {
           Intent intent= new Intent(this,CustomSetting.class);
            startActivity(intent);

        }
return super.onOptionsItemSelected(item);
    }

Detail_menu.xml

 <item android:id="@+id/text_option"
        android:orderInCategory="100"
        android:showAsAction="ifRoom"
        android:title="Text Option"
         />

CustomSetting.java

public class CustomSetting extends AppCompatActivity {

    DetailActivity detailActivity;
    ImageButton plus,minus,close;
    int txtSize = 14;
    TextView detail=detailActivity.detailtext;
 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.custom_setting);
        plus= (ImageButton) findViewById(R.id.plus);
        minus= (ImageButton) findViewById(R.id.minus);
        close= (ImageButton) findViewById(R.id.close);

plus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (detail.getTextSize() == 14 ||detail.getTextSize() == 15 || detail.getTextSize() == 16 || detail.getTextSize() == 17){
                    txtSize++;
                    detail.setTextSize(txtSize);
                } else if (detail.getTextSize() == 18) {
                    txtSize+= 0;
                    detail.setTextSize(txtSize);
                } else{
                    txtSize+= 0;
                    detail.setTextSize(txtSize);
                }

            }
        });
        minus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (detail.getTextSize() == 15||detail.getTextSize() ==16||detail.getTextSize() ==17|detail.getTextSize() ==18){
                    txtSize--;
                    detail.setTextSize(txtSize);
                } else {
                    txtSize += 0;
                    detail.setTextSize(txtSize);
                }

            }
        });
        close.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent= new Intent(CustomSetting.this,DetailActivity.class);
                startActivity(intent);
            }
        });

    }

custom_setting.xml

<ImageButton
    android:layout_width="50dp"
    android:layout_height="40dp"
    android:background="@drawable/close"
    android:layout_above="@+id/textView"
    android:layout_toRightOf="@+id/minus"
    android:layout_toEndOf="@+id/minus"
    android:id="@+id/close"
    />
    <ImageButton
        android:layout_width="50dp"
        android:layout_height="40dp"
        android:background="@drawable/plusign"
        android:layout_marginTop="110dp"
        android:id="@+id/plus"
        android:layout_alignParentTop="true"
        android:layout_alignLeft="@+id/textView"
        android:layout_alignStart="@+id/textView" />
    <ImageButton
        android:layout_width="50dp"
        android:layout_height="40dp"
        android:background="@drawable/minusign"
        android:id="@+id/minus"
        android:layout_alignTop="@+id/plus"
        android:layout_alignRight="@+id/textView"
        android:layout_alignEnd="@+id/textView" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Change Text Size"
        android:id="@+id/textView"
        android:layout_above="@+id/minus"
        android:layout_centerHorizontal="true"
        android:textColor="#FFFFFF"
        />

Logcat:

   Process: com.example.aa.sidd, PID: 23413
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.aa.sidd/com.example.aa.sidd.CustomSetting}: android.view.InflateException: Binary XML file line #17: Error inflating class <unknown>
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2436)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2498)
            at android.app.ActivityThread.access0(ActivityThread.java:179)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1324)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5641)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1288)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1104)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: android.view.InflateException: Binary XML file line #17: Error inflating class <unknown>
            at android.view.LayoutInflater.createView(LayoutInflater.java:626)

Answer 1

if (id==R.id.text_option)

但是菜单的 id 显示正确，如下所述

item android:id="@+id/display"

所以我觉得应该是

if (id==R.id.display) //like this

Answer 2

我假设您在 DetailActivity 中有一些行，例如

Textview detailtext;

改为

static Textview detailtext;

然后摆脱你的

DetailActivity detailActivity;

并更改行

TextView detail=detailActivity.detailtext;

到

TextView detail=DetailActivity.detailtext;

希望这对您有所帮助。

Answer 3

虽然这个问题已经被接受了答案，但是使用静态控件引用是不好的编程习惯。

相反，您有数据传递的意图，因此在打开 CustomSetting activity 时，您应该将 textview textsize 作为 intent 额外传递，如下所示：-

Intent intent= new Intent(this,CustomSetting.class);
intent.putExtra("textview_size",detailtext.getTextSize());
startActivity(intent);

在 CustomSetting onCreate 中你可以做

if (getIntent().hasExtra("textview_size"){
  font_size = getIntent().getFloatExtra("textview_size",<default_size_your_want>);
}

点击 + 或 - 按钮时，您可以使用

font_size += 1

或

fontsize -= 1

当点击关闭按钮时你可以做

Intent intent= new Intent(CustomSetting.this,DetailActivity.class);
intent.putExtra("textview_size",fontsize);
startActivity(intent);

并且在你的 DetailActivity oncreate 中你可以做

if (getIntent().hasExtra("textview_size"){
  font_size = getIntent().getFloatExtra("textview_size",<default_size_your_want>);
  detailtext.setTextSize(font_size);
}

Answer 4

三件事，
来自您的原始问题：
你会因为试图访问一个未初始化的对象而得到一个空指针异常。在这种情况下 activity.

DetailActivity detailActivity;
ImageButton plus,minus,close;
/.../
TextView detail=detailActivity.detailtext;

并且您尝试执行此操作的方式不可能实现您的尝试。请从一位著名的 android 专家那里看到这个 link。
which answers a similar question here Get reference of one Activity from another in android

另一个可能的问题是您的资源。您正在加载多个图像按钮，确保您的图像大小（字节）不会太大。

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.aa.sidd/com.example.aa.sidd.CustomSetting}: android.view.InflateException: Binary XML file line #17: Error inflating class

看到这个问题：
android.view.InflateException: Binary XML file line #12: Error inflating class <unknown>

第三，正如我在评论中提到的，我不认为将成员声明为静态作为解决方法是个好主意，请参阅此处 Avoiding memory leaks 静态成员、方法和类需要在计划任何应用程序时谨慎使用并考虑。用任何语言。嗯，这就是我的看法。

Answer 5

以DialogFragment 的形式显示新布局。这个想法是以 DialogFragment 弹出窗口的形式显示 increase/Decrease 选项。您可以从弹出窗口中 increase/decrease 大小。弹出窗口关闭后，所选大小将设置为 Activity 中的 TextView。

MainActivity.java

public class MainActivity extends AppCompatActivity {

public static int updatedSize;
TextView greetingText;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    greetingText = (TextView)findViewById(R.id.hello_world_text);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        mycustomLayout();
        return true;
    }

    return super.onOptionsItemSelected(item);
}

public void mycustomLayout(){
    FragmentManager manager = getFragmentManager();
    PopUp popUp = new PopUp(new FragmentDismissHandler());
    popUp.show(manager,"POPUP");

}

public void refreshText(){
    if( updatedSize>0)
    greetingText.setTextSize(updatedSize);
}

private class FragmentDismissHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        super.handleMessage(msg);
        refreshText();
    }
}

}

PopUp.java（自定义布局为 DialogFragment）

public class PopUp extends DialogFragment implements View.OnClickListener{

ImageButton increase,decrease,set;
TextView sizeOfText;
static int size;
Handler handler;


public PopUp(Handler handler) {
    this.handler = handler;
}
public PopUp(){

}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    getDialog().setTitle("change text size");
    View view = inflater.inflate(R.layout.my_custom_layout, container, false);

    increase = (ImageButton)view.findViewById(R.id.inc);
    increase.setOnClickListener(this);

    decrease = (ImageButton)view.findViewById(R.id.dec);
    decrease.setOnClickListener(this);

    sizeOfText = (TextView)view.findViewById(R.id.size_text);
    sizeOfText.setText("text");

    set = (ImageButton)view.findViewById(R.id.ok);
    set.setOnClickListener(this);

    size = (int) sizeOfText.getTextSize();

    return view;
}


@Override
public void onClick(View view) {
    int id= view.getId();

    if(id==R.id.inc){
        size = size +1;
        sizeOfText.setText("text");
        sizeOfText.setTextSize(size);
    }
    if(id== R.id.dec){
        size = size - 1;
        sizeOfText.setText("text");
        sizeOfText.setTextSize(size);
    }
    if(id== R.id.ok){
        dismiss();
    }
}

@Override
public void onDismiss(DialogInterface dialog) {
    super.onDismiss(dialog);
    MainActivity.updatedSize = size;
    handler.sendEmptyMessage(0);
}

}

尝试通过单击按钮更改 textView 中的文本大小时应用程序崩溃

App Crash When Trying to Change textsize in textView by clicking on button

android

menuitem

textview