在ProgressBar上加文字----显示百分比的进度条

　　一般的ProgressBar都只是一个光光的条（这里说的都是水平进度条），虽然比不用进度条时给用户的感觉要好，但是如果在形像化的东西上面再加上点文字，将进度描述量化，就可以让用户更加明白当前进度是多少了。

　　有了需求，就可以开始实现了。

　　这里的原理就是继承一个ProgressBar，然后重写里面的onDraw()方法。

　　不多说，直接上码。（下面代码中的 package hol.test; ，import就不写了）

    public class MyProgress extends ProgressBar{
        String text;
        Paint mPaint;
         
        public MyProgress(Context context) {
            super(context);
            // TODO Auto-generated constructor stub
            System.out.println("1");
            initText(); 
        }
         
        public MyProgress(Context context, AttributeSet attrs, int defStyle) {
            super(context, attrs, defStyle);
            // TODO Auto-generated constructor stub
            System.out.println("2");
            initText();
        }
     
     
        public MyProgress(Context context, AttributeSet attrs) {
            super(context, attrs);
            // TODO Auto-generated constructor stub
            System.out.println("3");
            initText();
        }
         
        @Override
        public synchronized void setProgress(int progress) {
            // TODO Auto-generated method stub
            setText(progress);
            super.setProgress(progress);
             
        }
     
        @Override
        protected synchronized void onDraw(Canvas canvas) {
            // TODO Auto-generated method stub
            super.onDraw(canvas);
            //this.setText();
            Rect rect = new Rect();
            this.mPaint.getTextBounds(this.text, 0, this.text.length(), rect);
            int x = (getWidth() / 2) - rect.centerX();  
            int y = (getHeight() / 2) - rect.centerY();  
            canvas.drawText(this.text, x, y, this.mPaint);  
        }
         
        //初始化，画笔
        private void initText(){
            this.mPaint = new Paint();
            this.mPaint.setColor(Color.WHITE);
             
        }
         
        private void setText(){
            setText(this.getProgress());
        }
         
        //设置文字内容
        private void setText(int progress){
            int i = (progress * 100)/this.getMax();
            this.text = String.valueOf(i) + "%";
        }
         
         
}

　　这样一个可以满足我们基本需求的进度条就写好了。

　　用的时候就可以直接在layout的XML里面加了，不过添加的写法稍微有点不同。标记名要写成这个自定义进度条的完整类名，就像下面这样。

<hol.test.MyProgress
       android:id="@+id/pgsBar"
       android:max="100"
       android:layout_width="fill_parent"
       android:layout_height="wrap_content"
       style="?android:attr/progressBarStyleHorizontal"
       android:visibility="visible"
       />

　　这样写后，可能会因为命名空间改变，下面属性无法用代码提示。一个简单的做法就是，先写一个正常的ProgressBar的标记，把属性写完后，再将ProgressBar替换为我们自定义的进度条的完整类名。

　　最后，使用方法就和普通的ProgressBar差不多了。

public class ProgressTest extends Activity {
     
    private Button btn_go = null;
    private MyProgress myProgress = null;
    private Handler mHandler;
     
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        findView();
        setParam();
        addListener();
         
        mHandler =  new Handler(new Callback() {
             
            @Override
            public boolean handleMessage(Message msg) {
                // TODO Auto-generated method stub
                myProgress.setProgress(msg.what);
                return false;
            }
        });
         
    }
     
    private void findView(){
        btn_go = (Button) findViewById(R.id.btn_go);
        myProgress = (MyProgress) findViewById(R.id.pgsBar);
    }
     
    private void setParam(){
        btn_go.setText("开始");
    }
    private void addListener(){
        btn_go.setOnClickListener(new OnClickListener() {
             
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                new Thread(new Runnable() { 
                    @Override
                    public void run() {
                        // TODO Auto-generated method stub
                        for(int i = 0;i <=50; i++){
                            mHandler.sendEmptyMessage(i * 2);
                            try {
                                Thread.sleep(80);
                            } catch (InterruptedException e) {
                                // TODO Auto-generated catch block
                                e.printStackTrace();
                            }
                        }
                    }
                }).start();
            }
        });
    }
}