Question

我在网上跟随教程，遇到一个问题，我正在努力找出Null对象在哪里，就像我在Android手机中设置动态壁纸时一样。只是说“不幸的是，晨动态壁纸已经停止”

我试图找出解决方案，但无法获得解决方案。即使我尝试调试代码，但应用程序也未得到调试。

import android.graphics.Canvas;
import android.graphics.Movie;
import android.service.wallpaper.WallpaperService;
import android.util.Log;
import android.view.SurfaceHolder;

import java.io.IOException;
import android.os.Handler;

public class GIFWallpaperService extends WallpaperService {
    @Override
    public WallpaperService.Engine onCreateEngine() {

            try{
                Movie movie = Movie.decodeStream(getResources().getAssets().open("image.gif"));
                System.out.println("This is 1111111111");
                return new GIFWallpaperEngine(movie);
            } catch (IOException e){
                Log.d("GIF", "Could not load Assets");
                return null;
            }


    }

    private class GIFWallpaperEngine extends WallpaperService.Engine{

        private final int frameDuration = 20;
        private SurfaceHolder holder;
        private Movie movie;
        private boolean visible;
        private Handler handler;

        public GIFWallpaperEngine(Movie movie){

            this.movie = movie;
            handler = new Handler();

        }
        public void onCreate(SurfaceHolder surfaceHolder){

            super.onCreate(surfaceHolder);
            this.holder = surfaceHolder;
            System.out.println("This is 2222");
        }

        private Runnable drawGIF = new Runnable() {
            @Override
            public void run() {
                draw();
            }
        };

        private void draw(){

            if(visible){

                Canvas canvas = holder.lockCanvas();
                canvas.save();
                canvas.scale(4f,4f);
                movie.draw(canvas,-100,0);
                canvas.restore();
                holder.unlockCanvasAndPost(canvas);
                movie.setTime((int)(System.currentTimeMillis() % movie.duration()));
                System.out.println("This is 333333");

                handler.removeCallbacks(drawGIF);
                handler.postDelayed (drawGIF,frameDuration);
            }
        }

        public void onVisibilityChanged(boolean visible){

            this.visible = visible;
            if(visible){

                handler.post(drawGIF);
            }else{
                handler.removeCallbacks(drawGIF);
            }
        }

        @Override
        public void onDestroy() {
            super.onDestroy();
            handler.removeCallbacks(drawGIF);
        }
    }

}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="livewallpaper.digital.com.morninglivewallpaper">

    <uses-feature
        android:name="android.software.live_wallpaper"
        android:required="true">
    </uses-feature>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <service android:name=".GIFWallpaperService"
                android:enabled="true"
                android:label="GIF Wallpaper"
                android:permission="android.permission.BIND_WALLPAPER">
            <intent-filter>
                <action android:name="android.service.wallpaper.WallpaperService" />
            </intent-filter>
            <meta-data
                android:name="android.service.wallpaper"
                android:resource="@xml/wallpaper">


            </meta-data>

        </service>
    </application>

</manifest>

这是Logcat

01-29 02:56:39.845 1308-1308/? D/dalvikvm: Late-enabling CheckJNI
01-29 02:56:39.857 1308-1308/? D/GIF: Could not load Assets
01-29 02:56:39.857 1308-1308/? D/AndroidRuntime: Shutting down VM
01-29 02:56:39.861 1308-1308/? W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0xa6147908)
01-29 02:56:39.861 1308-1314/? E/jdwp: Failed sending reply to debugger: Broken pipe
01-29 02:56:39.861 1308-1314/? D/dalvikvm: Debugger has detached; object registry had 1 entries
01-29 02:56:39.861 1308-1308/? E/AndroidRuntime: FATAL EXCEPTION: main
    java.lang.NullPointerException
        at android.service.wallpaper.WallpaperService$IWallpaperEngineWrapper.executeMessage(WallpaperService.java:1037)
        at com.android.internal.os.HandlerCaller$MyHandler.handleMessage(HandlerCaller.java:40)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:5041)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
        at dalvik.system.NativeStart.main(Native Method)

如何解决此问题？

Answer 1

     try{
            Movie movie = Movie.decodeStream(getResources().getAssets().open("image.gif"));
            System.out.println("This is 1111111111");
            return new GIFWallpaperEngine(movie);
        } catch (IOException e){
            Log.d("GIF", "Could not load Assets");
            return null;
        }

对该代码段进行一些调试，检查是否未发生异常，否则引擎实例将为null，也可能是您造成NPE的原因

空指针异常-动态壁纸

1 个答案: