Android之界面刷新 View更新 Invalidate和postInvalidate的区别
2016-06-01 14:44
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Android中实现view的更新有两组方法,一组是invalidate,另一组是postInvalidate,其中前者是在UI线程自身中使用,而后者在非UI线程中使用。
Android提供了Invalidate方法实现界面刷新,但是Invalidate不能直接在线程中调用,因为他是违背了单线程模型:Android UI操作并不是线程安全的,并且这些操作必须在UI线程中调用。
Android程序中可以使用的界面刷新方法有两种,分别是利用Handler和利用postInvalidate()来实现在线程中刷新界面。
1,利用invalidate()刷新界面
实例化一个Handler对象,并重写handleMessage方法调用invalidate()实现界面刷新;而在线程中通过sendMessage发送界面更新消息。
// 在onCreate()中开启线程
new Thread(new GameThread()).start();、
// 实例化一个handler
Handler myHandler = new Handler() {
// 接收到消息后处理
public void handleMessage(Message msg) {
switch (msg.what) {
case Activity01.REFRESH:
mGameView.invalidate(); // 刷新界面
break;
}
super.handleMessage(msg);
}
};
class GameThread implements Runnable {
public void run() {
while (!Thread.currentThread().isInterrupted()) {
Message message = new Message();
message.what = Activity01.REFRESH;
// 发送消息
Activity01.this.myHandler.sendMessage(message);
try {
Thread.sleep(100);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
}
}
2,使用postInvalidate()刷新界面
使用postInvalidate则比较简单,不需要handler,直接在线程中调用postInvalidate即可。
class GameThread implements Runnable {
public void run() {
while (!Thread.currentThread().isInterrupted()) {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
// 使用postInvalidate可以直接在线程中更新界面
mGameView.postInvalidate();
}
}
}
View 类中postInvalidate()方法源码如下,可见它也是用到了handler的:
public void postInvalidate() {
postInvalidateDelayed(0);
}
public void postInvalidateDelayed(long delayMilliseconds) {
// We try only with the AttachInfo because there's no point in invalidating
// if we are not attached to our window
if (mAttachInfo != null) {
Message msg = Message.obtain();
msg.what = AttachInfo.INVALIDATE_MSG;
msg.obj = this;
mAttachInfo.mHandler.sendMessageDelayed(msg, delayMilliseconds);
}
}
除了onCreate()是运行在UI线程上的,其实其他大部分方法都是运行在UI线程上的,其实其实只要你没有开启新的线程,你的代码基本上都运行在UI线程上。
完整例子:
package com.czz.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.os.Message;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;
public class KeyDownActivity extends Activity {
private static final int REFRESH = 0x00001;
GameView mGameView;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
mGameView = new GameView(this);
this.setContentView(mGameView);
new Thread(new GameThread()).start();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
toast("touch position: "+event.getX()+","+event.getY());
this.finish();
return super.onTouchEvent(event);
}
void toast(String text){
Toast.makeText(KeyDownActivity.this, text, Toast.LENGTH_SHORT).show();
}
private class GameThread implements Runnable {
@Override
public void run() {
// TODO Auto-generated method stub
while(!Thread.currentThread().isInterrupted()){
try{
Thread.sleep(400);
} catch(Exception e){
toast("GameThread error");
Thread.currentThread().interrupt();
}
//使用postInvalidate可以直接在线程中刷新
mGameView.postInvalidate();
}
}
}
private class GameThreadOld implements Runnable{
@Override
public void run() {
// TODO Auto-generated method stub
while(!Thread.currentThread().isInterrupted()){
try{
Thread.sleep(200);
} catch(Exception e){
toast("GameThread error");
Thread.currentThread().interrupt();
}
Message m = new Message();
m.what = KeyDownActivity.REFRESH;
KeyDownActivity.this.mHandler.sendMessage(m);
}
}
}
private Handler mHandler = new Handler(){
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
switch(msg.what){
case KeyDownActivity.REFRESH:
/*invalidate不能直接在线程中刷新,因为它违反了单线程模型:
Android的UI操作不是线程安全的,并且这些操作必须在UI线程中执行,
因此Android最常用的方法就是利用Handler来实现UI线程的刷新。*/
mGameView.invalidate();
break;
}
super.handleMessage(msg);
}
};
private class GameView extends View{
int mCount = 0;
int y = 100;
public GameView(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
@Override
public void draw(Canvas canvas) {
// TODO Auto-generated method stub
super.draw(canvas);
if(mCount < 10)
mCount++;
else
mCount = 0;
Paint mPaint = new Paint();
switch(mCount % 4){
case 0:mPaint.setColor(Color.RED);break;
case 1:mPaint.setColor(Color.GREEN);break;
case 2:mPaint.setColor(Color.BLUE);break;
case 3:mPaint.setColor(Color.YELLOW);break;
default:mPaint.setColor(Color.WHITE);break;
}
canvas.drawRect((480-80)/2, y, (480-80)/2+80, y+40, mPaint);
}
}
}
感谢http://www.cnblogs.com/tt_mc/archive/2012/01/30/2332023.html
感谢http://blog.csdn.net/vincent_czz/article/details/7018725
Android提供了Invalidate方法实现界面刷新,但是Invalidate不能直接在线程中调用,因为他是违背了单线程模型:Android UI操作并不是线程安全的,并且这些操作必须在UI线程中调用。
Android程序中可以使用的界面刷新方法有两种,分别是利用Handler和利用postInvalidate()来实现在线程中刷新界面。
1,利用invalidate()刷新界面
实例化一个Handler对象,并重写handleMessage方法调用invalidate()实现界面刷新;而在线程中通过sendMessage发送界面更新消息。
// 在onCreate()中开启线程
new Thread(new GameThread()).start();、
// 实例化一个handler
Handler myHandler = new Handler() {
// 接收到消息后处理
public void handleMessage(Message msg) {
switch (msg.what) {
case Activity01.REFRESH:
mGameView.invalidate(); // 刷新界面
break;
}
super.handleMessage(msg);
}
};
class GameThread implements Runnable {
public void run() {
while (!Thread.currentThread().isInterrupted()) {
Message message = new Message();
message.what = Activity01.REFRESH;
// 发送消息
Activity01.this.myHandler.sendMessage(message);
try {
Thread.sleep(100);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
}
}
2,使用postInvalidate()刷新界面
使用postInvalidate则比较简单,不需要handler,直接在线程中调用postInvalidate即可。
class GameThread implements Runnable {
public void run() {
while (!Thread.currentThread().isInterrupted()) {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
// 使用postInvalidate可以直接在线程中更新界面
mGameView.postInvalidate();
}
}
}
View 类中postInvalidate()方法源码如下,可见它也是用到了handler的:
public void postInvalidate() {
postInvalidateDelayed(0);
}
public void postInvalidateDelayed(long delayMilliseconds) {
// We try only with the AttachInfo because there's no point in invalidating
// if we are not attached to our window
if (mAttachInfo != null) {
Message msg = Message.obtain();
msg.what = AttachInfo.INVALIDATE_MSG;
msg.obj = this;
mAttachInfo.mHandler.sendMessageDelayed(msg, delayMilliseconds);
}
}
除了onCreate()是运行在UI线程上的,其实其他大部分方法都是运行在UI线程上的,其实其实只要你没有开启新的线程,你的代码基本上都运行在UI线程上。
完整例子:
package com.czz.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.os.Message;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;
public class KeyDownActivity extends Activity {
private static final int REFRESH = 0x00001;
GameView mGameView;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
mGameView = new GameView(this);
this.setContentView(mGameView);
new Thread(new GameThread()).start();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
toast("touch position: "+event.getX()+","+event.getY());
this.finish();
return super.onTouchEvent(event);
}
void toast(String text){
Toast.makeText(KeyDownActivity.this, text, Toast.LENGTH_SHORT).show();
}
private class GameThread implements Runnable {
@Override
public void run() {
// TODO Auto-generated method stub
while(!Thread.currentThread().isInterrupted()){
try{
Thread.sleep(400);
} catch(Exception e){
toast("GameThread error");
Thread.currentThread().interrupt();
}
//使用postInvalidate可以直接在线程中刷新
mGameView.postInvalidate();
}
}
}
private class GameThreadOld implements Runnable{
@Override
public void run() {
// TODO Auto-generated method stub
while(!Thread.currentThread().isInterrupted()){
try{
Thread.sleep(200);
} catch(Exception e){
toast("GameThread error");
Thread.currentThread().interrupt();
}
Message m = new Message();
m.what = KeyDownActivity.REFRESH;
KeyDownActivity.this.mHandler.sendMessage(m);
}
}
}
private Handler mHandler = new Handler(){
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
switch(msg.what){
case KeyDownActivity.REFRESH:
/*invalidate不能直接在线程中刷新,因为它违反了单线程模型:
Android的UI操作不是线程安全的,并且这些操作必须在UI线程中执行,
因此Android最常用的方法就是利用Handler来实现UI线程的刷新。*/
mGameView.invalidate();
break;
}
super.handleMessage(msg);
}
};
private class GameView extends View{
int mCount = 0;
int y = 100;
public GameView(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
@Override
public void draw(Canvas canvas) {
// TODO Auto-generated method stub
super.draw(canvas);
if(mCount < 10)
mCount++;
else
mCount = 0;
Paint mPaint = new Paint();
switch(mCount % 4){
case 0:mPaint.setColor(Color.RED);break;
case 1:mPaint.setColor(Color.GREEN);break;
case 2:mPaint.setColor(Color.BLUE);break;
case 3:mPaint.setColor(Color.YELLOW);break;
default:mPaint.setColor(Color.WHITE);break;
}
canvas.drawRect((480-80)/2, y, (480-80)/2+80, y+40, mPaint);
}
}
}
感谢http://www.cnblogs.com/tt_mc/archive/2012/01/30/2332023.html
感谢http://blog.csdn.net/vincent_czz/article/details/7018725
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