Android 通过广播来异步更新UI

时间：2023-03-09 23:49:14
Android 通过广播来异步更新UI

之前的项目里要做一个异步更新UI的功能，可是结果出现了ANR，所以想写个demo来測试究竟是哪个地方出现了问题，结果发现原来的思路是没有问题，郁闷Android 通过广播来异步更新UI~~

如今这个demo 就是模拟项目里面 的步骤

1、接收到系统的广播（如今模拟为人工发送）

2、广播接收到后，handler通知异步线程从网上下载数据，是异步（模拟为sleep）

3、数据下载完后handler再通知UI更新



以下是基本的两个代码，可以正确执行

package com.example.testanr;

import android.support.v7.app.ActionBarActivity;

import android.content.Intent;

import android.content.IntentFilter;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.TextView;

public class MainActivity extends ActionBarActivity {

	public 	TextView hellworld = null;

	public 	Button sendBroadcast = null;

	public final static String MY_ACTION = "com.example.testanr.MY_ACTION";

	public static int i = 0;

	public Handler updateUI  =new Handler(){

		@Override

		public void handleMessage(Message msg) {

			// TODO Auto-generated method stub

			super.handleMessage(msg);

			if(msg.arg1 ==0){

				hellworld.setText("更新UI - "+ i);

				i++;

			}

		}

	};

	public Handler mHandler =new Handler(){

		@Override

		public void handleMessage(Message msg) {

			// TODO Auto-generated method stub

			super.handleMessage(msg);

			if (msg.arg1 == 1  ){

				new Thread(new Runnable(){

					@Override

					public void run() {

						// TODO Auto-generated method stub

						System.out.println("Thread id is "+Thread.currentThread().getId()+",and Thread name is "+Thread.currentThread().getName());

						try {

							Thread.currentThread().sleep(15000);

						} catch (InterruptedException e) {

							// TODO Auto-generated catch block

							e.printStackTrace();

						}

						Message msg =new Message();

						msg.arg1 =0;

						updateUI.sendMessage(msg);

					}

				}).start();

			}

		}

	};

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        hellworld = (TextView)findViewById(R.id.hello_world);

        sendBroadcast = (Button)findViewById(R.id.sendBroadcast);

        //生成一个BroadcastReceiver对象

        TestReceiver  testReceiver = new TestReceiver(mHandler);

		//生成一个IntentFilter对象

		IntentFilter filter = new IntentFilter();

		filter.addAction(MainActivity.MY_ACTION);

		//将BroadcastReceiver对象注冊到系统其中

		MainActivity.this.registerReceiver(testReceiver, filter);

		System.out.println("Thread id is "+Thread.currentThread().getId()+",and Thread name is "+Thread.currentThread().getName());

        sendBroadcast.setOnClickListener(new OnClickListener(){

			@Override

			public void onClick(View v) {

				// TODO Auto-generated method stub

				//发送广播

				Intent intent = new Intent();

				intent.setAction(MainActivity.MY_ACTION);

                sendBroadcast(intent);

			}

        });

    }

    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.main, menu);

        return true;

    }

    @Override

    public boolean onOptionsItemSelected(MenuItem item) {

        // Handle action bar item clicks here. The action bar will

        // automatically handle clicks on the Home/Up button, so long

        // as you specify a parent activity in AndroidManifest.xml.

        int id = item.getItemId();

        if (id == R.id.action_settings) {

            return true;

        }

        return super.onOptionsItemSelected(item);

    }

}

还有reciever

package com.example.testanr;

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.os.Handler;

import android.os.Message;

public class TestReceiver extends BroadcastReceiver {

	public Handler handler;

	public Message message = null;

	public TestReceiver(Handler handler){

		this.handler = handler;

	}

	@Override

	public void onReceive(Context context, Intent intent) {

		// TODO Auto-generated method stub

		//这里每次都要new，否者会报错

		message = new Message();

		message.arg1 = 1;

		handler.sendMessage(message);

	}

}

如今才发现一个message是不能往MessageQueue里面发送多次的，否则会报这种错

java.lang.IllegalStateException: The specified message queue synchronization  barrier token has not been posted or has already been removed.

就说这个message的synchronization  barrier
token 已经发送过了的

可是项目里面的问题还没有解决，回头找出原因再发上来

我们知道ANR一般有三种类型：

1：KeyDispatchTimeout(5 seconds) --主要类型

按键或触摸事件在特定时间内无响应

2：BroadcastTimeout(10
seconds)

BroadcastReceiver在特定时间内无法处理完毕

3：ServiceTimeout(20 seconds) --小概率类型

Service在特定的时间内无法处理完毕

所以原因还是应该是另外一种，可能没有模拟对

ANR的分析

怎样调查并解决ANR

1：首先分析log

2: 从trace.txt文件查看调用stack.

3: 看代码

4：细致查看ANR的成因（iowait?block?memoryleak?）

可是项目里面log没有输出，是最奇怪的~~~

//************************************9-29更新****************8

回去一看果然是一个message往looper的messagequeue发送了多次！！！可是log没有输出exception，并且为什么会导致ANR，非常奇怪~~~求大神解答

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