Android UI更新
做过Android开发的人都遇到过这样的问题:随着需求的变化,某些入口界面会出现UI的增减、内容变化和跳转界面变化等问题,这里就说明几种方法来实现UI的更新。
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-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() { @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。
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