我在自定义的一个View上添加了一个Button,添加之后很正常,但问题是一旦为这个Button添加监听后,程序就挂了,控制台抛异常,琢磨半天没明白,还请坛友看看
Activity类:
public class ActivityMain extends Activity {
private Button btnOK;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); btnOK = (Button)findViewById(R.id.btn);
btnOK.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
}
});
this.setContentView(R.layout.main);
}
}layout:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<com.app.ViewMain
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_x="100dip"
android:layout_y="100dip"
android:text="@string/hello"/>
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="OK"
android:id="@+id/btn"/>
</FrameLayout>ViewMain:
public class ViewMain extends View { public ViewMain(Context context, AttributeSet attrs) { super(context, attrs);
} @Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.WHITE);
super.onDraw(canvas);
}
}问题就来自Activity中的
btnOK.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
}
});
不添加这段代码,程序没问题,但一旦添加,程序就挂了LogCat就会抛出如下信息:
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): FATAL EXCEPTION: main
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app/com.app.ActivityMain}: java.lang.NullPointerException
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.os.Handler.dispatchMessage(Handler.java:99)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.os.Looper.loop(Looper.java:123)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread.main(ActivityThread.java:4627)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at java.lang.reflect.Method.invokeNative(Native Method)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at java.lang.reflect.Method.invoke(Method.java:521)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at dalvik.system.NativeStart.main(Native Method)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): Caused by: java.lang.NullPointerException
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at com.app.ActivityMain.onCreate(ActivityMain.java:19)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): ... 11 more
Activity类:
public class ActivityMain extends Activity {
private Button btnOK;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); btnOK = (Button)findViewById(R.id.btn);
btnOK.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
}
});
this.setContentView(R.layout.main);
}
}layout:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<com.app.ViewMain
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_x="100dip"
android:layout_y="100dip"
android:text="@string/hello"/>
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="OK"
android:id="@+id/btn"/>
</FrameLayout>ViewMain:
public class ViewMain extends View { public ViewMain(Context context, AttributeSet attrs) { super(context, attrs);
} @Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.WHITE);
super.onDraw(canvas);
}
}问题就来自Activity中的
btnOK.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
}
});
不添加这段代码,程序没问题,但一旦添加,程序就挂了LogCat就会抛出如下信息:
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): FATAL EXCEPTION: main
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app/com.app.ActivityMain}: java.lang.NullPointerException
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.os.Handler.dispatchMessage(Handler.java:99)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.os.Looper.loop(Looper.java:123)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread.main(ActivityThread.java:4627)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at java.lang.reflect.Method.invokeNative(Native Method)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at java.lang.reflect.Method.invoke(Method.java:521)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at dalvik.system.NativeStart.main(Native Method)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): Caused by: java.lang.NullPointerException
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at com.app.ActivityMain.onCreate(ActivityMain.java:19)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
01-26 15:03:17.669: ERROR/AndroidRuntime(2197): ... 11 more
解决方案 »
- mac os x下编译android源码出错
- 如何处理ListView中有不同的Item?
- 蓝牙Socket通信问题
- html解析啊啊啊啊啊啊啊啊
- 在 android 上实现 自己的 flash player 方案
- 急,无法建立数据库,怎么回事?
- 台式摄像头采集到的视屏传到手机显示不清晰
- 安卓下的package目录去哪里下载啊
- 怎么实现运行时控件添加,拖拉,定位?
- 用apk安装时出现不能安装的提示。
- 求解!!100分!ubuntu下android源码mm编译带三方jar包的项目,javamail报错!errorIOException while sendin
- 100分求->如何在android手机上折线图,横轴为时间,纵轴为数字
btnOK.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
}
});
this.setContentView(R.layout.main);
顺序错了,应该是:
this.setContentView(R.layout.main);
btnOK = (Button)findViewById(R.id.btn);
btnOK.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
}
});
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
替换为:
import android.view.View;
import android.view.View.OnClickListener;
就可以了