public class ProgressView extends ImageView {  private Drawable maskDraw;  /**   * 加載的進度 0-100   */  private int mProcess = 20;  public ProgressView(Context context, AttributeSet attrs) {    super(context, attrs);    maskDraw = context.getResources().getDrawable(R.drawable.red_bg);  }  @Override  protected void onDraw(Canvas canvas) {    super.onDraw(canvas);    // 保存當前畫筆的狀態    canvas.save();    int topline = (int) (getHeight() - getHeight() * getProcess() / 100);    /*     * canvas 剪切出一個區域，使在這個區域里面的內容是有效的，區域之外是無效的。     */    canvas.clipRect(0, topline, getWidth(), getHeight());    maskDraw.draw(canvas);    // 恢復到之前保存的狀態    canvas.restore();  }  @Override  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    super.onMeasure(widthMeasureSpec, heightMeasureSpec);    maskDraw.setBounds(0, 0, getWidth(), getHeight());  }  public float getProcess() {    return mProcess;  }  /**   * 設置新的進度以后，自動刷新   */  public void setProgress(int mProcess) {    if (mProcess > 100) {      this.mProcess = 100;    }    if (mProcess < 0) {      this.mProcess = 0;    }    this.mProcess = mProcess;    invalidate();  }}

public class ProgressActivity extends Activity {  private ProgressView piv;  private int pivDeep = 0;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_progressview);    piv = (ProgressView) findViewById(R.id.my_pro_iv);    handler.sendEmptyMessage(2);  }  private Handler handler = new Handler() {    @Override    public void handleMessage(Message msg) {      switch (msg.what) {      case 1:        piv.setProgress(pivDeep);        break;      case 2:        new Thread() {          public void run() {            while (true) {              pivDeep = (pivDeep + 5) % 100;              handler.sendEmptyMessage(1);              try {                Thread.sleep(200);              } catch (InterruptedException e) {                e.printStackTrace();              }            }          };        }.start();        break;      default:        break;      }    }  };}