package com.example.battery;

import android.content.Context;

import android.content.res.Resources;

import android.graphics.Bitmap;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.drawable.BitmapDrawable;

import android.os.Handler;

import android.os.Message;

import android.util.AttributeSet;

import android.view.View;

public class Battery extends View {

	public float currentX = 80;

	public float currentY = 80;

	private float secondY = 80;

	private Paint mPaint = new Paint();

	private Context mContext;

	private Handler mHandler;

	private Bitmap mBmp;

	private int speedTime = 20;

	private float with = 200;

	private float height = 50;

	private float percentage = 0.5f;

	public Battery(Context context) {

		super(context);

		this.mContext = context;

	}

	public Battery(Context context, AttributeSet set) {

		super(context, set);

		this.mContext = context;

		init();

	}

	public void onDraw(Canvas canvas) {

		super.onDraw(canvas);

		with = this.getWidth();

		height = this.getHeight();

		mPaint.setColor(Color.BLUE);

		Resources res = mContext.getResources();

		BitmapDrawable bmpDraw = (BitmapDrawable) res

				.getDrawable(R.drawable.loading_pic);

		mBmp = bmpDraw.getBitmap();

		canvas.clipRect(0, 0, with*percentage, height);

		canvas.drawBitmap(mBmp, 0, currentY, mPaint);

		canvas.drawBitmap(mBmp, 0, secondY, mPaint);

	}

	private void init() {

		percentage = 0;

		mHandler = new Handler() {

			public void handleMessage(Message msg) {

				switch (msg.what) {

				case 1:

					currentX ++;

					currentY ++;

					if (mBmp != null && currentY > mBmp.getHeight()){

						currentY = -mBmp.getHeight();

					}

					if (mBmp != null){

						secondY = currentY+mBmp.getHeight();

						if (secondY >= mBmp.getHeight()){

							secondY = currentY-mBmp.getHeight();

						}

					}

					percentage = percentage + 0.003f;

					if (percentage > 1){

						percentage = 0;

					}

					// 每次计算后都发送消息进入下一次循环，并刷新界面

					mHandler.sendEmptyMessageDelayed(1, speedTime);

					postInvalidate();

					break;

				}

				super.handleMessage(msg);

				postInvalidate();

			}

		};

		// 首次循环刷新界面

		mHandler.sendEmptyMessageDelayed(1, speedTime);

	}

}

package com.example.battery;

import android.app.Activity;

import android.os.Bundle;

public class MainActivity extends Activity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

    }

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:layout_gravity="center"

    android:gravity="center" >  

    <com.example.battery.Battery

        android:layout_width="300dp"

        android:layout_height="10dp"

        android:layout_gravity="center"

        android:gravity="center"

        android:padding="10dp" />  

</LinearLayout>