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Android子线程真的不能更新UI?

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:

  1. 使用Handler消息传递机制;
  2. 使用AsyncTask异步任务;
  3. 使用runOnUiThread(action)方法;
  4. 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

package com.example.runonuithreadtest;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;
public class MainActivity extends Activity {
	private TextView tv;
	Handler handler = new Handler()
	{
		public void handleMessage(android.os.Message msg) {
			if(msg.what==0x123)
			{
				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(0x123);
		}
	}
}

2. 使用AsyncTask异步任务

  • 注:更新UI的操作只能在onPostExecute(String result)方法中。
package com.example.runonuithreadtest;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.TextView;
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

package com.example.runonuithreadtest;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
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

package com.example.runonuithreadtest;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;
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");
			}
		});
	}
}


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