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当点击其他标签上的其他按钮时，允许点击按钮

分类: 技术问答 • 2022-06-26 15:19:53
问题描述：

在我的Android应用程序中，我有两个选项卡。第一个选项卡包含一个名为“保存”的按钮，我已经将其设置为btn.setEnable(false)。当点击其他标签上的其他按钮时，允许点击按钮

在第二个选项卡上，我有一个“清除”按钮。

所以我打算做的是当我点击“清除”按钮，我想要“保存”按钮可点击。

下面的代码是显示何时单击“清除”按钮。

  public void Clear(View view) { 
       StringBuilder text = new StringBuilder(); 


       try { 

        InputStream instream = openFileInput("myfile.txt"); 

        if (instream != null) {    

        InputStreamReader inputreader = new InputStreamReader(instream); 
        BufferedReader buffreader = new BufferedReader(inputreader); 

        File dir = getFilesDir(); 
        File file = new File(dir, "myfile.txt"); 
        boolean delete = file.delete(); 


         } 


        } 

         catch (IOException e) { 
          e.printStackTrace(); 
         } 
         Button btn=(Button)findViewById(R.id.Save); btn.setEnabled(true); 
         TextView myTextView = (TextView) findViewById(R.id.TextView1); 
         myTextView.setText(""); 

      } 
}

不理会我的TODO的代码......我迷惑约我应该在哪里把这个代码导致我的

Button btn=(Button)findViewById(R.id.Save); 
btn.setEnabled(true);

结果到应用程序强制关闭，logcat中显示什么。 任何帮助将不胜感激。由于

尝试： 根据维克拉姆后，我点击 “清除” 按钮，应用力关闭 logcat的：

07-25 13:15:02.430: W/System.err(4739): java.io.FileNotFoundException: /data/data/com.example.androidtablayout/files/myfile.txt: open failed: ENOENT (No such file or directory) 
07-25 13:15:02.445: W/System.err(4739):  at libcore.io.IoBridge.open(IoBridge.java:406) 
07-25 13:15:02.445: W/System.err(4739):  at java.io.FileInputStream.<init>(FileInputStream.java:78) 
07-25 13:15:02.445: W/System.err(4739):  at android.app.ContextImpl.openFileInput(ContextImpl.java:673) 
07-25 13:15:02.445: W/System.err(4739):  at android.content.ContextWrapper.openFileInput(ContextWrapper.java:159) 
07-25 13:15:02.445: W/System.err(4739):  at com.example.androidtablayout.HistoryActivity.ViewText(HistoryActivity.java:114) 
07-25 13:15:02.445: W/System.err(4739):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-25 13:15:02.445: W/System.err(4739):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-25 13:15:02.445: W/System.err(4739):  at android.view.View$1.onClick(View.java:3064) 
07-25 13:15:02.445: W/System.err(4739):  at android.view.View.performClick(View.java:3591) 
07-25 13:15:02.445: W/System.err(4739):  at android.view.View$PerformClick.run(View.java:14263) 
07-25 13:15:02.445: W/System.err(4739):  at android.os.Handler.handleCallback(Handler.java:605) 
07-25 13:15:02.445: W/System.err(4739):  at android.os.Handler.dispatchMessage(Handler.java:92) 
07-25 13:15:02.445: W/System.err(4739):  at android.os.Looper.loop(Looper.java:137) 
07-25 13:15:02.445: W/System.err(4739):  at android.app.ActivityThread.main(ActivityThread.java:4507) 
07-25 13:15:02.450: W/System.err(4739):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-25 13:15:02.450: W/System.err(4739):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-25 13:15:02.455: W/System.err(4739):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790) 
07-25 13:15:02.455: W/System.err(4739):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557) 
07-25 13:15:02.455: W/System.err(4739):  at dalvik.system.NativeStart.main(Native Method) 
07-25 13:15:02.455: W/System.err(4739): Caused by: libcore.io.ErrnoException: open failed: ENOENT (No such file or directory) 
07-25 13:15:02.460: D/dalvikvm(4739): GC_CONCURRENT freed 112K, 3% free 9418K/9671K, paused 2ms+2ms 
07-25 13:15:02.460: W/System.err(4739):  at libcore.io.Posix.open(Native Method) 
07-25 13:15:02.460: W/System.err(4739):  at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110) 
07-25 13:15:02.460: W/System.err(4739):  at libcore.io.IoBridge.open(IoBridge.java:390) 
07-25 13:15:02.460: W/System.err(4739):  ... 18 more 
07-25 13:15:03.730: D/Network(4739): Network 
07-25 13:15:03.940: D/Network(4739): Network 
07-25 13:15:04.140: D/Network(4739): Network 
07-25 13:15:04.335: D/Network(4739): Network 
07-25 13:15:08.215: D/AndroidRuntime(4739): Shutting down VM 
07-25 13:15:08.215: W/dalvikvm(4739): threadid=1: thread exiting with uncaught exception (group=0x40c3e1f8) 
07-25 13:15:08.220: E/AndroidRuntime(4739): FATAL EXCEPTION: main 
07-25 13:15:08.220: E/AndroidRuntime(4739): java.lang.IllegalStateException: Could not execute method of the activity 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at android.view.View$1.onClick(View.java:3069) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at android.view.View.performClick(View.java:3591) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at android.view.View$PerformClick.run(View.java:14263) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at android.os.Handler.handleCallback(Handler.java:605) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at android.os.Handler.dispatchMessage(Handler.java:92) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at android.os.Looper.loop(Looper.java:137) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at android.app.ActivityThread.main(ActivityThread.java:4507) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at dalvik.system.NativeStart.main(Native Method) 
07-25 13:15:08.220: E/AndroidRuntime(4739): Caused by: java.lang.reflect.InvocationTargetException 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at android.view.View$1.onClick(View.java:3064) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  ... 11 more 
07-25 13:15:08.220: E/AndroidRuntime(4739): Caused by: java.lang.NullPointerException 
07-25 13:15:08.220: E/AndroidRuntime(4739):  at com.example.androidtablayout.HistoryActivity.Clear(HistoryActivity.java:172) 
07-25 13:15:08.220: E/AndroidRuntime(4739):  ... 14 more

Acoording到Tarsem，应用力收：

* *

07-25 13:25:56.960: D/Network(6667): Network 
07-25 13:25:57.000: D/dalvikvm(6667): GC_CONCURRENT freed 112K, 3% free 9417K/9671K, paused 2ms+3ms 
07-25 13:25:57.155: D/Network(6667): Network 
07-25 13:25:57.315: D/Network(6667): Network 
07-25 13:25:57.440: D/Network(6667): Network 
07-25 13:25:59.010: D/AndroidRuntime(6667): Shutting down VM 
07-25 13:25:59.010: W/dalvikvm(6667): threadid=1: thread exiting with uncaught exception (group=0x40c3e1f8) 
07-25 13:25:59.020: E/AndroidRuntime(6667): FATAL EXCEPTION: main 
07-25 13:25:59.020: E/AndroidRuntime(6667): java.lang.IllegalStateException: Could not execute method of the activity 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at android.view.View$1.onClick(View.java:3069) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at android.view.View.performClick(View.java:3591) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at android.view.View$PerformClick.run(View.java:14263) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at android.os.Handler.handleCallback(Handler.java:605) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at android.os.Handler.dispatchMessage(Handler.java:92) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at android.os.Looper.loop(Looper.java:137) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at android.app.ActivityThread.main(ActivityThread.java:4507) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at dalvik.system.NativeStart.main(Native Method) 
07-25 13:25:59.020: E/AndroidRuntime(6667): Caused by: java.lang.reflect.InvocationTargetException 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at java.lang.reflect.Method.invoke(Method.java:511) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at android.view.View$1.onClick(View.java:3064) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  ... 11 more 
07-25 13:25:59.020: E/AndroidRuntime(6667): Caused by: java.lang.NullPointerException 
07-25 13:25:59.020: E/AndroidRuntime(6667):  at com.example.androidtablayout.HistoryActivity.Clear(HistoryActivity.java:171) 
07-25 13:25:59.020: E/AndroidRuntime(6667):  ... 14 more

**

答

在类的开头声明你的按钮（任何特定的方法外）：

Button btn;

在onCreate(Bundle)初始化你的按钮：

btn = (Button) findViewById(R.id.Save); 

// Diable the button 
btn.setEnabled(false);

更改Clear(View)到：

public void Clear(View view) { 
      StringBuilder text = new StringBuilder(); 

      try { 
       InputStream instream = openFileInput("myfile.txt"); 

       if (instream != null) {    

       InputStreamReader inputreader = new InputStreamReader(instream); 
       BufferedReader buffreader = new BufferedReader(inputreader); 

       File dir = getFilesDir(); 
       File file = new File(dir, "myfile.txt"); 
       boolean delete = file.delete(); 
        } 
       } 
        catch (IOException e) { 
         e.printStackTrace(); 
        } 

        btn.setEnabled(true); 
        TextView myTextView = (TextView) findViewById(R.id.TextView1); 
        myTextView.setText(""); 
     }

}

答

由于NullPointerException的原因，你的应用程序正在关闭。

07-25 13:15:08.220: E/AndroidRuntime(4739): at com.example.androidtablayout.HistoryActivity.Clear(HistoryActivity.java:172)

请参阅logcat的......

的解决办法是改变以下两个行...

Button btn= (Button)findViewById(R.id.Save); btn.setEnabled(true); 
TextView myTextView = (TextView) findViewById(R.id.TextView1);

到...

Button btn= (Button) view.findViewById(R.id.Save); btn.setEnabled(true); 
TextView myTextView = (TextView) view.findViewById(R.id.TextView1);

按@ vikram的建议，移动Clear方法以外的声明。将它们声明为全局变量，以便它们可以在类中的任何地方使用。

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