1、Activity的 runOnUiThread
textView = (TextView) findViewById( R.id.tv );
new Thread(new Runnable() {
@Override
public void run() {
runOnUiThread(new Runnable() {
@Override
public 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( ) {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
textView.setText( "Ui更新了");
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView = (TextView) findViewById( R.id.tv );
new Thread(new Runnable() {
@Override
public 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();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView = (TextView) findViewById( R.id.tv );
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep( 2000 );
} catch (InterruptedException e) {
e.printStackTrace();
}
handler.post(new Runnable() {
@Override
public void run() {
textView.setText( "Ui更新了");
}
}) ;
}
}).start();
}
}
在子线程中切换到主线程
new Thread(new Runnable() {
@Override
public void run() {
LogUtil.d( "ttt 11111111111" + Thread.currentThread().getName() );
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public 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-155
ttt 22222222222Thread-155
ttt 33333333333Thread-155
ttt 44444444444Thread-155
ttt 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() {
@Override
public void run() {
try {
Thread.sleep( 2000 );
} catch (InterruptedException e) {
e.printStackTrace();
}
textView.post(new Runnable() {
@Override
public 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。