Android异步更新

大家都知道由于性能要求，android要求只能在UI线程中更新UI，要想在其他线程中更新UI，我大致总结了4种方式，欢迎补充纠正：

使用Handler消息传递机制;

使用AsyncTask异步任务;

使用runOnUiThread(action)方法;

使用Handler的post(Runnabel r)方法;

下面分别使用四种方式来更新一个TextView。

1.使用Handler消息传递机制

public class MainActivity extends Activity {
    private TextView tv;
    Handler handler = new Handler()
    {
        public void handleMessage(android.os.Message msg) {
          
                tv.setText("更新后的TextView");
            
        };
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView) findViewById(R.id.tv);
        new MyThread().start();
    }
    class MyThread extends Thread
    {
        @Override
        public void run() {
            //延迟两秒更新
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            handler.sendEmptyMessage();
        }
    }
}

2.使用AsyncTask异步任务

注：更新UI的操作只能在onPostExecute(String result)方法中。

public class MainActivity extends Activity {
    private TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView) findViewById(R.id.tv);
        new Yibu().execute();
    }
    class Yibu extends AsyncTask<String, String, String>
    {
        @Override
        protected String doInBackground(String... params) {
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return null;
        }
        @Override
        protected void onPostExecute(String result) {
            // TODO Auto-generated method stub
            tv.setText("更新后的TextView");
        }
    }
}

3.使用runOnUiThread(action)方法

public class MainActivity extends Activity {
    private TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView) findViewById(R.id.tv);
        new MyThread().start();
    }
    class MyThread extends Thread
    {
        @Override
        public void run() {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    // TODO Auto-generated method stub
                        try {
                            //延迟两秒更新
                            Thread.sleep(2000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        tv.setText("更新后的TextView");
                }
            });
        }
    }
}

4.使用Handler的post(Runnabel r)方法

public class MainActivity extends Activity {
    private TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView) findViewById(R.id.tv);
        Handler handler = new Handler();
        handler.post(new Runnable(){
            @Override
            public void run() {
                try {
                    //延迟两秒更新
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                tv.setText("更新后的TextView");
            }
        });
    }
}