android 启动动画的渐变

一.启动动画的渐变：

    以后可能会用到的启动动画的效果：

效果图：

主界面：

public class MainActivity extends Activity {
    private LandingView lv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_main);
        lv = new LandingView(this);
		// 将自定义视图显示在本界面
		setContentView(lv);
		// 创建修改Logo透明度的异步任务
		LoGoTask task = new LoGoTask(this,lv);
		// 执行异步任务
		task.execute();
    }
}

public class LoGoTask extends AsyncTask<Object, Integer, String> {
	// 当前的透明度取值
	int alpha = 0;
	MainActivity main;
	private LandingView lv;
	public LoGoTask(MainActivity main,LandingView lv){
		this.main = main;
		this.lv = lv;
	}
	@Override
	protected void onPreExecute() {
		// TODO Auto-generated method stub
		super.onPreExecute();
	}
	/**
	 * 异步任务执行成功后，自动跳转至应用程序主界面
	 * */
	@Override
	protected void onPostExecute(String result) {
		    Intent intent=new Intent(main, TestActivity.class);
		    main.startActivity(intent);
		    main.finish();
	}
	/**
	 * 修改Logo自定义视图图片透明度，并重绘
	 * */
	@Override
	protected void onProgressUpdate(Integer... values) {
		int temp = values[0].intValue();
		lv.redraw(temp);
	}
	/**
	 * 异步任务，循环改变透明度取值
	 * */
	@Override
	protected String doInBackground(Object... arg0) {
		// TODO Auto-generated method stub
		while (alpha < 255) {
			try {
				Thread.sleep(100);
				publishProgress(new Integer(alpha));
				alpha += 5;
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		return null;
	}
}

public class LandingView extends View{
	    
		private  int alpha = 0;
		
		private Bitmap logo;
		private Context context;
		public LandingView(Context context) {
			super(context);
			this.context = context;
			logo = BitmapFactory.decodeResource(context.getResources(),
					R.drawable.background1);
		}
		public void redraw(int aplha){
	       this.alpha = aplha;
	       invalidate();
		}
		@Override
		protected void onDraw(Canvas canvas) {
			// TODO Auto-generated method stub
			super.onDraw(canvas);
			// 清屏
			canvas.drawColor(Color.WHITE);
			// 创建画笔对象
			Paint p = new Paint();
			// 设置画笔对象的透明度为当前透明度取值
			p.setAlpha(alpha);
			WindowManager manager = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
			DisplayMetrics dm=new DisplayMetrics();
			manager.getDefaultDisplay().getMetrics(dm);
			int width2=dm.widthPixels;
			int height2=dm.heightPixels;
			// 在视图上利用画笔绘制Logo图像
			RectF rect = new RectF(0,0,width2,height2);
			canvas.drawBitmap(logo, null, rect, p);
		}
}

public class TestActivity extends Activity{
	 @Override
	    protected void onCreate(Bundle savedInstanceState) {
	        super.onCreate(savedInstanceState);
	        setContentView(R.layout.activity_main);

	    }
}

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

</LinearLayout>