IMageSwitcher.setImageResource()中的空点异常

时间:2013-11-13 09:43:31

标签: android drawable android-image imageswitcher

我正在制作一个动画,以便在ImageSwitcher中显示许多图像,但我仍然坚持将图像设置为ImageSwitcher

这是我xml中的imageswitcher。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_margin="10dp"
        android:src="@drawable/logo" />

    <ImageSwitcher
        android:id="@+id/switcher"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ImageSwitcher>

</LinearLayout>

这是我的代码

setContentView(R.layout.main_screen);

    final int[] imgs = {R.drawable.m1,
        R.drawable.m2,
        R.drawable.m3,
        R.drawable.m4,
        R.drawable.m5,
        R.drawable.m6};

    imgswitcher = (ImageSwitcher) findViewById(R.id.switcher);
    imgswitcher.postDelayed(new Runnable() 
    {
        int index = 0;
        @Override
        public void run() 
        {
            imgswitcher.setImageResource(imgs[index]);
            if(index==(imgs.length-1))
                 index = 0;
            else
                 index++;
            imgswitcher.postDelayed(this, 1000);
        }
    }, 1000);

我在“imgswitcher.setImageResource(imgs[index]);

行上收到错误

错误

11-13 15:08:34.574: E/AndroidRuntime(5258): FATAL EXCEPTION: main
11-13 15:08:34.574: E/AndroidRuntime(5258): java.lang.NullPointerException
11-13 15:08:34.574: E/AndroidRuntime(5258):     at android.widget.ImageSwitcher.setImageResource(ImageSwitcher.java:41)
11-13 15:08:34.574: E/AndroidRuntime(5258):     at com.example.imageswitcher.MainActivity$1.run(MainActivity.java:33)
11-13 15:08:34.574: E/AndroidRuntime(5258):     at android.os.Handler.handleCallback(Handler.java:587)
11-13 15:08:34.574: E/AndroidRuntime(5258):     at android.os.Handler.dispatchMessage(Handler.java:92)
11-13 15:08:34.574: E/AndroidRuntime(5258):     at android.os.Looper.loop(Looper.java:123)
11-13 15:08:34.574: E/AndroidRuntime(5258):     at android.app.ActivityThread.main(ActivityThread.java:3683)
11-13 15:08:34.574: E/AndroidRuntime(5258):     at java.lang.reflect.Method.invokeNative(Native Method)
11-13 15:08:34.574: E/AndroidRuntime(5258):     at java.lang.reflect.Method.invoke(Method.java:507)
11-13 15:08:34.574: E/AndroidRuntime(5258):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11-13 15:08:34.574: E/AndroidRuntime(5258):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
11-13 15:08:34.574: E/AndroidRuntime(5258):     at dalvik.system.NativeStart.main(Native Method)

我甚至在没有Runnable仅仅为ImageSwitcher分配抽奖的情况下尝试了它,但我面临同样的问题。任何帮助将不胜感激。

3 个答案:

答案 0 :(得分:8)

imgswitcher.setFactory(this);

缺少

修改 问题作者给出了进一步的解决方案:

public MyActivity implements ViewSwitcher.ViewFactory

@Override
public View makeView() {
    ImageView imageView = new ImageView(this);
    imageView.setBackgroundColor(0xFF000000);
    imageView.setScaleType(ImageView.ScaleType.CENTER);
    imageView.setLayoutParams(
        new ImageSwitcher.LayoutParams(
            LayoutParams.MATCH_PARENT,
            LayoutParams.WRAP_CONTENT));
    return imageView;
}

使用setFactory设置工厂还有其他选择。阅读ViewSwitcher docs

答案 1 :(得分:0)

希望对您有帮助。

重写onViewCreated方法,然后将ImageSwitcher放入其中。即

public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    mImageSwitcher.setImageResource(image[index]);

}

答案 2 :(得分:0)

那是因为您需要在调用imageSwitcher.setImageResource之前先在imageSwitcher上调用imageSwitcher.setFacotry,只需使用以下代码即可:

 imageSwitcher.setFactory(new ViewFactory() {
       public View makeView() {
          ImageView myView = new ImageView(getApplicationContext());
          return myView;
       }
    }
//then you can call setImageResource
imageSwitcher.setImageResource(R.drawable.my_image);