我正在创建一个动态壁纸应用程序，其中有一个随机的图片幻灯片以及底部的小缩略图，可以点击。我不得不扩展多个课程，我认为这就是我卡住的地方。请帮忙。
动态壁纸类：
import android.content.SharedPreferences;
import android.os.Bundle;
import android.os.Handler;
import android.service.wallpaper.WallpaperService;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.View;
import android.widget.AdapterView;
public class LiveWallpaper extends WallpaperService{
public static final String SHARED_PREFS_NAME = "livewallpapersettings";
@Override
public void onCreate() {
// TODO Auto-generated method stub
super.onCreate();
}
@Override
public void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
}
@Override
public Engine onCreateEngine() {
// TODO Auto-generated method stub
return new TestPatternEngine();
}
class TestPatternEngine extends Engine implements
SharedPreferences.OnSharedPreferenceChangeListener
{
/*Instance variables.*/
private AdapterView parent;
private View v;
private int position;
private long id;
private Bundle savedInstanceState;
private final Handler mHandler = new Handler();
private MainActivity mMainActivity;
private boolean mVisible;
private String mMode = "random";
private String mTransition = "fade";
private float mTouchX = -1;
private float mTouchY = -1;
private SharedPreferences mPreferences;
private final Runnable mStartApp = new Runnable(){
public void run() {
mMainActivity = new MainActivity();
mMainActivity.onCreate(savedInstanceState);
}
};
TestPatternEngine() {
mPreferences = LiveWallpaper.this.getSharedPreferences(SHARED_PREFS_NAME, 0);
mPreferences.registerOnSharedPreferenceChangeListener(this);
onSharedPreferenceChanged(mPreferences,null);
}
@Override
public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
// TODO Auto-generated method stub
mMode = prefs.getString("livewallpaper_mode", "random");
mTransition = prefs.getString("livewallpaper_transitions", "fade");
}
@Override
public void onCreate(SurfaceHolder surfaceHolder) {
// TODO Auto-generated method stub
super.onCreate(surfaceHolder);
setTouchEventsEnabled(true);
}
@Override
public void onDestroy()
{
super.onDestroy();
mHandler.removeCallbacks(mStartApp);
}
@Override
public void onVisibilityChanged(boolean visible)
{
mVisible = visible;
if (visible)
{
mMainActivity.onCreate(savedInstanceState);
}
else
{
mHandler.removeCallbacks(mStartApp);
}
}
@Override
public void onTouchEvent(MotionEvent event)
{
if (event.getAction() == MotionEvent.ACTION_MOVE)
{
mTouchX = event.getX();
mTouchY = event.getY();
}
else
{
mTouchX = -1;
mTouchY = -1;
}
super.onTouchEvent(event);
}
}
}
主要活动类：
import java.util.Random;
import java.util.Timer;
import java.util.TimerTask;
import com.example.LiveWallpaper.LiveWallpaper.TestPatternEngine;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.animation.AnimationUtils;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.Gallery.LayoutParams;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.ViewSwitcher;
public class MainActivity extends Activity implements
AdapterView.OnItemSelectedListener,ViewSwitcher.ViewFactory{
private final Handler mHandler = new Handler();
private int position =0;
@Override
public void onCreate(Bundle savedInstanceState) {
int delay = 1000;
int period = 3000;
Timer timer = new Timer();
timer.schedule(new TimerTask(){
@Override
public void run() {
// TODO Auto-generated method stub
runOnUiThread(new Runnable(){
@Override
public void run() {
// TODO Auto-generated method stub
Random rand = new Random();
position = rand.nextInt(mImageIds.length);
mSwitcher.setImageResource(mImageIds[position]);
}
});
}
}, delay, period);
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
mSwitcher = (ImageSwitcher) findViewById(R.id.switcher);
mSwitcher.setFactory(this);
mSwitcher.setInAnimation(AnimationUtils.loadAnimation(this,
android.R.anim.fade_in));
mSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this,
android.R.anim.fade_out));
Gallery g = (Gallery) findViewById(R.id.gallery);
g.setAdapter(new ImageAdapter(this));
g.setOnItemSelectedListener(this);
}
public void onItemSelected(AdapterView parent, View v, int position, long id) {
mSwitcher.setImageResource(mImageIds[position]);
}
public void onNothingSelected(AdapterView parent) {
}
public View makeView() {
ImageView i = new ImageView(this);
i.setBackgroundColor(0xFF000000);
i.setScaleType(ImageView.ScaleType.FIT_CENTER);
i.setLayoutParams(new ImageSwitcher.LayoutParams(
LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
return i;
}
private ImageSwitcher mSwitcher;
public class ImageAdapter extends BaseAdapter {
public ImageAdapter(Context c) {
mContext = c;
}
public int getCount() {
return mThumbIds.length;
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
ImageView i = new ImageView(mContext);
i.setImageResource(mThumbIds[position]);
i.setAdjustViewBounds(true);
i.setLayoutParams(new Gallery.LayoutParams(
LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
i.setBackgroundResource(R.drawable.ic_launcher);
return i;
}
private Context mContext;
}
private Integer[] mThumbIds = { R.drawable.image1, R.drawable.image2, R.drawable.image3, R.drawable.image4, R.drawable.image5 };
private Integer[] mImageIds = { R.drawable.image1,
R.drawable.image2, R.drawable.image3, R.drawable.image4, R.drawable.image5};
日志猫：
06-18 13:57:49.534: W/dalvikvm(283): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
06-18 13:57:49.584: E/AndroidRuntime(283): FATAL EXCEPTION: main
06-18 13:57:49.584: E/AndroidRuntime(283): java.lang.NullPointerException
06-18 13:57:49.584: E/AndroidRuntime(283): at com.example.Livewallpaper.LiveWallpaper$TestPatternEngine.onVisibilityChanged(LiveWallpaper.java:96)
06-18 13:57:49.584: E/AndroidRuntime(283): at android.service.wallpaper.WallpaperService$Engine.reportVisibility(WallpaperService.java:637)
06-18 13:57:49.584: E/AndroidRuntime(283): at android.service.wallpaper.WallpaperService$Engine.doVisibilityChanged(WallpaperService.java :620)
06-18 13:57:49.584: E/AndroidRuntime(283): at android.service.wallpaper.WallpaperService$IWallpaperEngineWrapper.executeMessage(WallpaperService.java:835)
06-18 13:57:49.584: E/AndroidRuntime(283): at com.android.internal.os.HandlerCaller$MyHandler.handleMessage(HandlerCaller.java:61)
06-18 13:57:49.584: E/AndroidRuntime(283): at android.os.Handler.dispatchMessage(Handler.java:99)
06-18 13:57:49.584: E/AndroidRuntime(283): at android.os.Looper.loop(Looper.java:123)
06-18 13:57:49.584: E/AndroidRuntime(283): at android.app.ActivityThread.main(ActivityThread.java:4627)
06-18 13:57:49.584: E/AndroidRuntime(283): at java.lang.reflect.Method.invokeNative(Native Method)
06-18 13:57:49.584: E/AndroidRuntime(283): at java.lang.reflect.Method.invoke(Method.java:521)
06-18 13:57:49.584: E/AndroidRuntime(283): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
06-18 13:57:49.584: E/AndroidRuntime(283): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
06-18 13:57:49.584: E/AndroidRuntime(283): at dalvik.system.NativeStart.main(Native Method)