Question

我是Android编程的新手。我正在构建一个应用程序，其中我有一个按钮，通过该按钮可以在点击时打开新活动。但是，当我点击该按钮时，应用程序停止，并且“不幸的是，它已关闭”。

这是我的java文件和清单代码的代码。

package com.example.jamaattiming;

//import android.view.View.OnClickListener;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
//import android.content.ComponentName;
import android.view.Menu;
import android.view.View;
//import android.content.Context;
import android.widget.Button;

public class MainPage extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_page);

        Button Qibla=(Button) findViewById(R.id.btnQibla);
        Qibla.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                //startActivity(new Intent("com.example.COMPASS"));
                    Intent intent = new Intent(MainPage.this, Qibla.class);
                    startActivity(intent);
            }
        }); 
    }

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

清单：

  <activity
    android:name=".Qibla"
    android:label="@string/app_name"
    android:screenOrientation="portrait" >  
  </activity>`

这是LogCat错误。

    12-29 14:45:31.810: I/Process(1705): Sending signal. PID: 1705 SIG: 9
    12-29 14:53:11.880: D/dalvikvm(1756): GC_FOR_ALLOC freed 62K, 7% free 2845K/3028K, paused 35ms, total 37ms
    12-29 14:53:11.880: I/dalvikvm-heap(1756): Grow heap (frag case) to 3.612MB for 756788-byte allocation
    12-29 14:53:11.941: D/dalvikvm(1756): GC_FOR_ALLOC freed 2K, 5% free 3581K/3768K, paused 52ms, total 53ms
    12-29 14:53:12.420: D/gralloc_goldfish(1756): Emulator without GPU emulation detected.
    12-29 14:53:17.419: D/dalvikvm(1756): GC_FOR_ALLOC freed 13K, 4% free 3639K/3772K, paused 189ms, total 211ms
    12-29 14:53:17.469: I/dalvikvm-heap(1756): Grow heap (frag case) to 4.568MB for 945616-byte allocation
    12-29 14:53:17.720: D/dalvikvm(1756): GC_FOR_ALLOC freed 1K, 3% free 4561K/4696K, paused 224ms, total 224ms
    12-29 14:53:20.159: I/Choreographer(1756): Skipped 35 frames!  The application may be doing too much work on its main thread.
    12-29 14:53:22.749: D/AndroidRuntime(1756): Shutting down VM
    12-29 14:53:22.780: W/dalvikvm(1756): threadid=1: thread exiting with uncaught exception (group=0x414c4700)
    12-29 14:53:22.960: E/AndroidRuntime(1756): FATAL EXCEPTION: main
    12-29 14:53:22.960: E/AndroidRuntime(1756): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.jamaattiming/com.example.jamaattiming.Qibla}: java.lang.ClassCastException: com.example.jamaattiming.Qibla cannot be cast to android.app.Activity
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2137)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at android.os.Handler.dispatchMessage(Handler.java:99)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at android.os.Looper.loop(Looper.java:137)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at android.app.ActivityThread.main(ActivityThread.java:5103)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at java.lang.reflect.Method.invokeNative(Native Method)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at java.lang.reflect.Method.invoke(Method.java:525)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at dalvik.system.NativeStart.main(Native Method)
    12-29 14:53:22.960: E/AndroidRuntime(1756): Caused by: java.lang.ClassCastException: com.example.jamaattiming.Qibla cannot be cast to android.app.Activity
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2128)
    12-29 14:53:22.960: E/AndroidRuntime(1756):     ... 11 more
    12-29 14:53:26.179: I/Process(1756): Sending signal. PID: 1756 SIG: 9

Answer 1

您的按钮对象必须setOncCickListner而不是其ID。使用此：

btn.setOnClickListener(new View.OnClickListener()

而不是：

 Qibla.setOnClickListener(new View.OnClickListener()

Answer 2

尝试

 Btn.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                    Intent intent = new Intent(MainPage.this, Compass.class);
                    startActivity(intent);
            }
        });

Answer 3

这样做

 Button Qibla =(Button) findViewById(R.id.btnQibla);

而不是

Button Btn=(Button) findViewById(R.id.btnQibla);

我希望您已在清单文件中定义指南针活动！

你为什么评论以下一行？

// import android.view.View.OnClickListener;

Answer 4

更改

Qibla.setOnClickListener(new View.OnClickListener() {

到

btn.setOnClickListener(new View.OnClickListener() {

应用程序在运行时关闭

4 个答案: