现在需要实现一个工具类，RunUtils，这个类中包含runOnUiThread(Context context, Runnable runnable)和runOnUiThreadBlock(Context context, Runnable runnable)两个方法。两个方法都使runnable在UI线程执行，runOnUiThread立即返回，runOnUiThreadBlock等待runnable执行完毕后才返回。
根据context创建一个Handler，这个Handler用于发送消息。runOnUiThread这个方法不需要同步，runOnUiThreadBlock需要同步。
RunUtils内容
package com.letv.handlertest; import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.util.Log; import java.lang.ref.WeakReference; public class RunUtils { private static final int WHAT_BLOCK = 0x1001; private static WeakReference<Context> weakContext;
private static WeakReference<Handler> weakHandler;
private static Object lock = new Object(); private static void init(Context context){
if(RunUtils.weakContext == null ||
(RunUtils.weakContext!=null && RunUtils.weakContext.get()!=context) ){
RunUtils.weakContext = new WeakReference<Context>(context); Handler handler = new Handler(context.getMainLooper()) {
@Override
public void dispatchMessage(Message msg) {
if(msg.what == WHAT_BLOCK){
Log.i(MainActivity.TAG, "what block");
synchronized (lock){
super.dispatchMessage(msg);
lock.notify();
Log.i(MainActivity.TAG, "notify");
}
}
else{
super.dispatchMessage(msg);
Log.i(MainActivity.TAG, "what not block");
}
}
};
weakHandler = new WeakReference<Handler>(handler);
handler = null;
}
} public static void runOnUiThread(Context context, Runnable runnable){
init(context);
weakHandler.get().post(runnable);
Log.i(MainActivity.TAG, "run ui over!");
} public static void runOnUiThreadBlock(Context context, Runnable runnable){
init(context); Message msg = Message.obtain(weakHandler.get(), runnable);
msg.what = WHAT_BLOCK;
msg.sendToTarget(); synchronized (lock){
Log.i(MainActivity.TAG, "begin wait!");
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
Log.i(MainActivity.TAG, "run ui block over!");
}
} }
主类MainActivity内容
package com.letv.handlertest; import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView; public class MainActivity extends Activity implements View.OnClickListener { public static final String TAG = "HandlerTest"; private Button btnRunOnUiThread, btnRunOnUiThreadBlock;
private TextView tvShow1, tvShow2;
// private RunUtilsB utils; @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView(); // utils = new RunUtilsB(this);
} private void initView(){
btnRunOnUiThread = (Button)findViewById(R.id.btnRunOnUiThread);
btnRunOnUiThreadBlock = (Button)findViewById(R.id.btnRunOnUiThreadBlock);
tvShow1 = (TextView)findViewById(R.id.tvShow1);
tvShow2 = (TextView)findViewById(R.id.tvShow2); btnRunOnUiThread.setOnClickListener(this);
btnRunOnUiThreadBlock.setOnClickListener(this);
} private void runUi(){
new Thread(new Runnable() {
@Override
public void run() {
RunUtils.runOnUiThread(MainActivity.this, new Runnable() {
@Override
public void run() {
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
tvShow1.setText("run ui");
}
});
}
}).start();
} private void runUiBlock(){
new Thread(new Runnable() {
@Override
public void run() {
RunUtils.runOnUiThreadBlock(MainActivity.this, new Runnable() {
@Override
public void run() {
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
tvShow2.setText("run ui block");
}
});
}
}).start();
} @Override
public void onClick(View v) {
if(v == btnRunOnUiThread){
runUi();
}
else if(v == btnRunOnUiThreadBlock){
runUiBlock();
}
}
}
运行结果正常。点击RunOnUiThread实现2s后更新textView1的值，点击调用后立马返回，点击RunOnUiThreadBlock后实现2s后更新textView2的值，更新完后才返回。