Question

package com.ave;

import com.ave.R;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageButton;



public class Menu extends Activity{
ImageButton select;    
int isClicked = 0;


        @Override
        protected void onCreate(Bundle savedInstanceState) {
                // TODO Auto-generated method stub
                super.onCreate(savedInstanceState);
                setContentView(R.layout.main);

                select = (ImageButton)findViewById(R.id.select);
        select.setOnClickListener(new OnClickListener() {

                public void onClick(View v) {
                     if (isClicked == 0){
                        select.setImageResource(R.drawable.select_pressed);
                        isClicked = 1;
                     }
                     else{
                        select.setImageResource(R.drawable.select);
                        isClicked = 0;
                     }
                }});
        }

        ImageButton audio;    
        int isClicked1 = 0;{

        audio = (ImageButton)findViewById(R.id.audio);
        audio.setOnClickListener(new OnClickListener() {

                public void onClick(View v) {
                     if (isClicked1 == 0){
                        audio.setImageResource(R.drawable.audio_pressed);
                        isClicked1 = 1;
                     }
                     else{
                        audio.setImageResource(R.drawable.audio);
                        isClicked1 = 0;
                     }
                 }
           });
         }
      }

============ logcat的=================

E AndroidRuntime: FATAL EXCEPTION: main
E AndroidRuntime: java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.ave/com.ave.Menu}: java.lang.NullPointerException
E AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1618)
E AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1716)
E AndroidRuntime:     at android.app.ActivityThread.access$1500(ActivityThread.java:124)
E AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:968)
E AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99)
E AndroidRuntime:     at android.os.Looper.loop(Looper.java:123)
E AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:3806)
E AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
E AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:507)
E AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
E AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
E AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
E AndroidRuntime: Caused by: java.lang.NullPointerException
E AndroidRuntime:     at android.app.Activity.findViewById(Activity.java:1693)
E AndroidRuntime:     at com.ave.Menu.(Menu.java:41)
E AndroidRuntime:     at java.lang.Class.newInstanceImpl(Native Method)
E AndroidRuntime:     at java.lang.Class.newInstance(Class.java:1409)
E AndroidRuntime:     at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
E AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1610)
E AndroidRuntime: ... 11 more

我在xml或类中没有错误，所有内容都被正确引用但是当我尝试通过AVD或我的手机测试应用程序时，它会在启动画面后停止。并生成您在LogCat中看到的内容。同样，xml或类中没有错误，并引用了所有内容。那我做错了什么？或者需要添加什么。添加第二个imageButton方法后，它都停止了工作，但如果我删除它。它工作正常。

  <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/droid_background">
    <TextView 
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center_horizontal"
    android:text="@string/hello"
    android:textColor="#FFFFFF"
    android:textStyle="bold"/>
    <ImageButton 
android:src="@drawable/select"
android:id="@+id/select"
android:layout_height="30dp"
android:layout_width="120dp"
android:background="@null"
    android:layout_alignParentLeft="true"
android:layout_alignParentBottom="true"/>
    <ImageButton
android:src="@drawable/audio"
android:id="@+id/audio"
android:layout_height="30dp"
android:layout_width="120dp"
android:background="@null"
android:layout_alignParentRight="true"
android:layout_alignParentBottom="true"/>
    </RelativeLayout>'

Answer 1

您是否尝试过“清理”项目？有时需要重新生成XML布局，以便app能够按预期工作。

Answer 2

您是否已将活动添加到AndroidManifest.xml文件中？

Answer 3

你有两个带有id音频的ImageButtons。尝试重命名一个。

测试后，应用程序强制关闭

3 个答案: