Android UI更新的几种方法总结

 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-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