自定义ProcessBar

android与其他GUI应用开发一样&＃xff0c;也提供了自定义控件的定制。本文中给出一个自定义processbar的例子&＃xff0c;如下&＃xff1a;

例子中&＃xff0c;控件能够定义进度条已实现和未实现的颜色属性&＃xff0c;并且用asynctask以每秒一格的速度刷新。

1. 在values下增加attr.xml&＃xff0c;定义MyProcessBar的属性

 2. 实现自定义的MyProcessBar类

public class MyProcessbar extends View {private Paint mPaint;private int current &＃61; 0;private int end &＃61; 10;private int color1;private int color2;public MyProcessbar(Context context, AttributeSet attrs) {super(context, attrs);mPaint &＃61; new Paint();TypedArray a &＃61; context.obtainStyledAttributes(attrs, R.styleable.MyProcessbar); color1 &＃61; a.getColor(R.styleable.MyProcessbar_color1,0); color2 &＃61; a.getColor(R.styleable.MyProcessbar_color2,0); a.recycle();}public MyProcessbar(Context context) {super(context);mPaint &＃61; new Paint();}//用以更新ProcessBarpublic void setCurAndEnd(int cur, int end){current &＃61; cur;end &＃61; end;invalidate();}&＃64;Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);mPaint.setStyle(Style.FILL);mPaint.setColor(color1);for(int i &＃61; 0; i }

 3. 在layout中使用该自定义控件

 4. 在Activity中启动一个异步任务更新该控件&＃xff0c;异步任务实现如下&＃xff1a;

public class MyTask extends AsyncTask {private MyProcessbar mprogressbar;public MyTask(MyProcessbar mprogressbar) {super();this.mprogressbar &＃61; mprogressbar;}&＃64;Overrideprotected String doInBackground(String... params) {int i &＃61; 0;for(i &＃61; 0; i <10; i&＃43;&＃43;){try {Thread.sleep(1000);publishProgress(i); } catch (InterruptedException e) {e.printStackTrace();}}return i &＃43; "&" &＃43; params[0];}&＃64;Overrideprotected void onProgressUpdate(Integer... values) {mprogressbar.setCurAndEnd(values[0], 10);}
}

备注&＃xff1a;

自定义控件此例中主要用到onDraw方法&＃xff0c;其他主要接口还有onMeasure和onLayout&＃xff0c;

1. onMeasure 属于View的方法&＃xff0c;用来测量自己和内容的来确定宽度和高度 &＃xff0c;view的measure方法体中会调用onMeasure

2. onLayout 属于ViewGroup的方法&＃xff0c;用来为当前ViewGroup的子元素的位置和大小