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[操作系统]Android 更新UI的几种方式

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();  }}

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。