1、Activity的 runOnUiThread    textView = (TextView) findViewById( R.id.tv );new Thread(new Runnable() {@Overridepublic void run() {runOnUiThread(new Runnable() {@Overridepublic void run() {textView.setText( "更新UI了");}});}}).start();

android Activity runOnUiThread() 方法使用

 

2、Handler sendEmptyMessage()

package lib.com.myapplication;import android.os.Handler; import android.os.Message; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.widget.TextView;public class MainActivity extends AppCompatActivity {private TextView textView ;Handler handler = new Handler( ) {@Overridepublic void handleMessage(Message msg) {super.handleMessage(msg);textView.setText( "Ui更新了");}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);textView = (TextView) findViewById( R.id.tv );new Thread(new Runnable() {@Overridepublic void run() {try {Thread.sleep( 2000 );} catch (InterruptedException e) {e.printStackTrace();}handler.sendEmptyMessage( 2 ) ;}}).start();} }

3、Handler  post()

package lib.com.myapplication; import android.os.Bundle; import android.os.Handler; import android.support.v7.app.AppCompatActivity; import android.widget.TextView;public class MainActivity extends AppCompatActivity {private TextView textView ;Handler handler = new Handler();@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);textView = (TextView) findViewById( R.id.tv );new Thread(new Runnable() {@Overridepublic void run() {try {Thread.sleep( 2000 );} catch (InterruptedException e) {e.printStackTrace();}handler.post(new Runnable() {@Overridepublic void run() {textView.setText( "Ui更新了");}}) ;}}).start();} }

在子线程中切换到主线程

new Thread(new Runnable() {@Overridepublic void run() {LogUtil.d( "ttt 11111111111" + Thread.currentThread().getName() );new Handler(Looper.getMainLooper()).post(new Runnable() {@Overridepublic void run() {LogUtil.d( "ttt 55555555" + Thread.currentThread().getName() );}});LogUtil.d( "ttt 22222222222" + Thread.currentThread().getName() );LogUtil.d( "ttt 33333333333" + Thread.currentThread().getName() );LogUtil.d( "ttt 44444444444" + Thread.currentThread().getName() );}}).start();

　　结果

ttt 11111111111Thread-155ttt 22222222222Thread-155ttt 33333333333Thread-155ttt 44444444444Thread-155ttt 55555555main

　　可见这种方式可以快速切换线程，从log日志来看，切换到主线程不会阻塞子线程。

 

4、view Post()　

textView = (TextView) findViewById( R.id.tv );new Thread(new Runnable() {@Overridepublic void run() {try {Thread.sleep( 2000 );} catch (InterruptedException e) {e.printStackTrace();}textView.post(new Runnable() {@Overridepublic void run() {textView.setText( "Ui更新了");}}) ;}}).start();

总结：

1、其实上面的四种方式都可归结于一种方式：handler 用于Android线程之间的通信。

2、为什么android要求只能在UI线程进行UI操作？ 主要还是为了避免多线程造成的并发的问题。在单线程操作UI是安全的。

 

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