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发表时间：2009-07-29
文字程序很简单，一个View，一个Activity，利用handler和postInvalidate()更新UI。 程序效果是一个蓝色的正方形向右移出屏幕。 package com.ray.test;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
public class TestHandler extends Activity {
private MyView myView;
private Handler mHandler;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myView = new MyView(this);
mHandler = new Handler();
mHandler.post(update);
setContentView(myView);
}
private Runnable update = new Runnable() {
public void run() {
myView.update();
mHandler.postDelayed(update, 5);
}
};
class MyView extends View{
private float x = 0f;
public MyView(Context context) {
super(context);
}
public void update(){
postInvalidate();
}
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
x+=1;
Paint mPaint = new Paint();
mPaint.setColor(Color.BLUE);
canvas.drawRect(x, 40, x+40, 80, mPaint);
}
}
}
之前还写过另外一篇关于Handler更新UI的文章： 声明：ITeye文章版权属于作者，受法律保护。没有作者书面许可不得转载。
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发表时间：2009-08-04
你的两篇文章对于invalidate()和postInvalidate()认识有些问题
http://www.iteye.com/topic/435147 http://rayleung.iteye.com/blog/411860 调用Handler.post(Runnable r)方法,Runnable运行在UI所在线程,所以可以直接调用View.invalidate() package com.ray.test;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
public class TestHandler extends Activity {
private MyView myView;
private Handler mHandler;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myView = new MyView(this);
mHandler = new Handler();
mHandler.post(new Runnable(){
@Override
public void run() {
myView.invalidate();
mHandler.postDelayed(this, 5);
}
});
setContentView(myView);
}
class MyView extends View{
private float x = 0f;
public MyView(Context context) {
super(context);
}
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
x+=1;
Paint mPaint = new Paint();
mPaint.setColor(Color.BLUE);
canvas.drawRect(x, 40, x+40, 80, mPaint);
}
}
}
在新线程里更新UI,可以直接postInvalidate() public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
myView = new MyView(this);
this.setContentView(this.myView);
new Thread(new myThread()).start();
}
class myThread implements Runnable {
public void run() {
while (!Thread.currentThread().isInterrupted()) {
try {
myView.postInvalidate();
Thread.sleep(100);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
}
}
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发表时间：2009-08-04
非常感谢您指出我理解上的错误，谢谢！我会继续努力的！
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