利用Handler更新Android UI的另一种方法
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。
Java代码
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);
}
}
}
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：
http://rayleung.iteye.com/blog/411860
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