Question

当我在eclipse的模拟器中启动我的活动时，遗憾的是我已经停止了应用程序的消息。希望知道问题出在哪里，我不明白LogCat我的logCat说：

06-10 21:13:06.769: I/Process(1158): Sending signal. PID: 1158 SIG: 9
06-10 21:13:21.609: D/AndroidRuntime(1197): Shutting down VM
06-10 21:13:21.609: W/dalvikvm(1197): threadid=1: thread exiting with uncaught exception (group=0xb4a96ba8)
06-10 21:13:21.679: E/AndroidRuntime(1197): FATAL EXCEPTION: main
06-10 21:13:21.679: E/AndroidRuntime(1197): Process: com.example.holamundo1, PID: 1197
06-10 21:13:21.679: E/AndroidRuntime(1197): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.holamundo1/com.example.holamundo1.MainActivity}: java.lang.NullPointerException
06-10 21:13:21.679: E/AndroidRuntime(1197):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at android.os.Handler.dispatchMessage(Handler.java:102)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at android.os.Looper.loop(Looper.java:136)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at android.app.ActivityThread.main(ActivityThread.java:5017)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at java.lang.reflect.Method.invokeNative(Native Method)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at java.lang.reflect.Method.invoke(Method.java:515)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at dalvik.system.NativeStart.main(Native Method)
06-10 21:13:21.679: E/AndroidRuntime(1197): Caused by: java.lang.NullPointerException
06-10 21:13:21.679: E/AndroidRuntime(1197):     at com.example.holamundo1.MainActivity.onCreate(MainActivity.java:15)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at android.app.Activity.performCreate(Activity.java:5231)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
06-10 21:13:21.679: E/AndroidRuntime(1197):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
06-10 21:13:21.679: E/AndroidRuntime(1197):     ... 11 more
06-10 21:13:25.819: I/Process(1197): Sending signal. PID: 1197 SIG: 9

代码是：

  package com.example.holamundo1;

  import android.os.Bundle;
  import android.app.*;
  import android.view.*;
  import android.widget.*;

  public class MainActivity extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Button miBoton = (Button)findViewById(R.id.button);
    miBoton.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            System.out.println("Botón presionado!");
        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu){
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}
   }

Answer 1

首先检查您的Button是否已导入import android.widget.Button;

检查Button的第二件事是activity_main.xml文件，其ID为R.id.button

Answer 2

activity_main.xml应该有一个ID为“button”

的按钮小部件

miBoton null ，因为button

中可能没有ID为“activity_main.xml”的小部件

重命名 xml中定义的按钮ID为“button”

或者

使用xml 中定义的按钮ID，比如它是否在xml中定义为button1，然后在您的代码中将其用作R.id.button1

Answer 3

在activity_main.xml文件中定义按钮ID。

不幸的是，应用已停止

3 个答案: