Question

当删除视图时，发生错误，我找不到错误的原因：

**java:**

  package com.test;
    import android.app.Activity;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.View;
    import android.view.ViewGroup;
    import android.view.animation.AlphaAnimation;
    import android.view.animation.Animation;
    import android.view.animation.Animation.AnimationListener;
    import android.widget.ImageView;

    public class AnimationActivity extends Activity {
        ImageView imageView = null;
        ViewGroup viewGroup = null;
        /** Called when the activity is first created. */
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);
            imageView = (ImageView)findViewById(R.id.imageviewID);
            viewGroup = (ViewGroup)findViewById(R.id.layoutId); 
        }
        public void buttonOnclick(View e){
            int id = e.getId();
            if(id==R.id.alpha){
                AlphaAnimation alphaAnimation = new AlphaAnimation(1.0f, 0f);
                alphaAnimation.setDuration(5000);
                alphaAnimation.setStartOffset(500);
                alphaAnimation.setFillAfter(true);
                alphaAnimation.setFillBefore(false);
                alphaAnimation.setAnimationListener(new RemoveAnimationListener());
                imageView.startAnimation(alphaAnimation);
                Log.d("mydebug","imageView------------>"+imageView);
                Log.d("mydebug","viewGroup------------>"+viewGroup);
            }
        }
        private class RemoveAnimationListener implements AnimationListener{

            @Override
            public void onAnimationEnd(Animation animation) {
                // TODO Auto-generated method stub
                viewGroup.removeView(imageView);

            }
            @Override
            public void onAnimationRepeat(Animation animation) {
                // TODO Auto-generated method stub

            }

            @Override
            public void onAnimationStart(Animation animation) {
                // TODO Auto-generated method stub

            }
        }
    }

以下是错误：

  05-22 10:01:16.367: W/dalvikvm(1839): threadid=1: thread exiting with uncaught exception (group=0x4001d7c8)ss
    05-22 10:01:16.397: E/AndroidRuntime(1839): FATAL EXCEPTION: main
    05-22 10:01:16.397: E/AndroidRuntime(1839): java.lang.NullPointerException
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1366)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.ViewGroup.drawChild(ViewGroup.java:1638)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.View.draw(View.java:6743)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.widget.FrameLayout.draw(FrameLayout.java:352)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.ViewGroup.drawChild(ViewGroup.java:1640)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.ViewGroup.drawChild(ViewGroup.java:1638)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.View.draw(View.java:6743)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.widget.FrameLayout.draw(FrameLayout.java:352)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1857)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.ViewRoot.draw(ViewRoot.java:1407)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1163)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.os.Handler.dispatchMessage(Handler.java:99)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.os.Looper.loop(Looper.java:123)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at android.app.ActivityThread.main(ActivityThread.java:4627)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at java.lang.reflect.Method.invokeNative(Native Method)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at java.lang.reflect.Method.invoke(Method.java:521)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
    05-22 10:01:16.397: E/AndroidRuntime(1839):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

您在buttononclick课程中使用了AnimationActivity方法。所以，如果你有提到哪个按钮点击你的XML文件然后很好。如果你没有提到
在XML中点击哪个按钮，那么你必须在你的活动中提到哪个按钮单击以便进行相应的方法调用。还有一件事是，如果没有找到视图组，以便显示空指针异常。您正在尝试访问或使用视图组，其值为null或未找到。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layoutId"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <ImageView android:id="@+id/imageviewID"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher"
        android:contentDescription="@string/app_name"
        android:paddingBottom="50dip"
        />
    <Button android:id="@+id/alpha"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/alpha"
        android:onClick="buttonOnclick"
        android:layout_below="@id/imageviewID"
        />
</RelativeLayout>

Answer 2

首先按下按钮，viewgroup将删除imageview，然后viewgroup不包括Imageview;如果您第二次按下按钮，则imageview为null，因此您无法从viewgroup中删除imageview。

如何删除android中的视图

2 个答案: