本文主要是介绍常用的两种handler调用方法,希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!
一、Handler、Thread、HandlerThread三者之间的关系如下:
1、Handler:在android中负责发送和处理消息,通过它可以实现其他支线线程与主线程之间的消息通讯。
2、Thread:Java进程中执行运算的最小单位,亦即执行处理机调度的基本单位。某一进程中一路单独运行的程序。
3、HandlerThread:一个继承自Thread的类HandlerThread。
二、Handler跟Thread结合使用,首先在FirstHandler.java类中创建要在界面调用的getSum方法,具体实现如下:
package com.example.handlerdemo;import android.os.Handler;
import android.os.Message;public class FirstHandler {private Handler mHandler;public static final int ADD_FLAG = 1;public void setHandler(Handler handler){mHandler = handler;}public synchronized void getSum(final int a, final int b){Logger.d("a = " + a + " ,b = " + b);class AddRunThread implements Runnable{@Overridepublic void run() {Logger.d("FirstHandler ThreadId = " + Thread.currentThread().getId());int sum = add(a, b); try {Thread.sleep(6 * 1000); //模拟加法运算是一个非常复杂的运算,所以要开线程} catch (InterruptedException e) {e.printStackTrace();}String result = "result = " + sum;Message message = mHandler.obtainMessage();message.what = ADD_FLAG;message.obj = result;mHandler.sendMessage(message); //在新的线程中进行发送Message消息}}Thread addRun = new Thread(new AddRunThread());addRun.setPriority(Thread.MAX_PRIORITY); //设置线程优先级addRun.start();//线程启动}/*** 实现加法运算*/private int add(int a, int b){return a + b;}
}
当调用 getSum方法的时候会先启动addRun线程,addRun线程启动后就会执行AddRunThread类里面的run方法,run方法里面执行了一个加法运算的add方法,然后会执行Thread.sleep(6 * 1000)来模拟耗时的操作。加法运算add方法实行结束后会通过mHandler.sendMessage(message)来通知界面更新信息。接下来看一下界面MainActivity的实现,具体如下:
package com.example.handlerdemo;import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.TextView;public class MainActivity extends Activity {private TextView textView;private FirstHandler firstHandler;private SecondHandler secondHandler;private String result;private Handler handler = new Handler(){public void handleMessage(android.os.Message msg) {Logger.d("Handler ThreadId = " + Thread.currentThread().getId());switch (msg.what) {case FirstHandler.ADD_FLAG:Logger.d("FirstHandler.ADD_FLAG");textView.setText((String) msg.obj); //更新加法运算后的结果break;case SecondHandler.UI_REFLESH:Logger.d("SecondHandler.UI_REFLESH"); textView.setText((String) msg.obj); //更新减法运算后的结果break;default:break;}};};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);Logger.d("main ThreadId = " + Thread.currentThread().getId());setContentView(R.layout.activity_main);textView = (TextView) findViewById(R.id.tx_show);firstHandler = new FirstHandler();secondHandler = new SecondHandler();}/** handler跟Thread结合使用的测试方法*/public void addCheck(View view){Logger.d();firstHandler.setHandler(handler); //设置Handler对象实例firstHandler.getSum(3000, 4600); //调用FirstHandler类的getSum方法}/** handler跟HandlerThread结合使用的测试方法*/public void decreaseClick(View view){Logger.d();secondHandler.getSerialThread().post(new Runnable() {@Overridepublic void run() {Logger.d("SecondHandler ThreadId = " + Thread.currentThread().getId());int sum = decrease(300, 180);try {Thread.sleep(8 * 1000); //模拟减法运算是一个非常复杂的运算,所以要开线程} catch (InterruptedException e) {e.printStackTrace();}result = "result2 = " + sum;Message message = new Message();message.what = SecondHandler.UI_REFLESH;message.obj = result;handler.sendMessage(message); //通过主线程更新UI}});}//减法运算private int decrease(int a, int b){return a - b;}}
可以看到在handleMessage中进行了消息处理,当msg.what等于FirstHandler.ADD_FLAG时,就会将加法运算的结果设置到textView中展示。
三、handler跟HandlerThread结合使用。代码逻辑主要在SecondHandler.java类中实现,具体如下:
package com.example.handlerdemo;import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;public class SecondHandler {public Handler uiHandler = new Handler(Looper.getMainLooper()); //main主线程,由于更新UI更新private HandlerThread mHandlerThread;private Handler handler;public static final int UI_REFLESH = 0X02;//设置handler对象关联public void setUIhandler(Handler handler){uiHandler = handler;}/***获取获得Looper对象的Handler实例*/public synchronized Handler getSerialThread(){if (null == mHandlerThread){HandlerThread thread = new HandlerThread("work_thread");//工作线程,用于耗时的操作,不能用于更新UIthread.start();handler = new Handler(thread.getLooper()){};}return handler;}
}
通过 new Handler(thread.getLooper())来建立handler跟HandlerThread的联系。接下来看一下具体怎么调用getSerialThread()方法,如下:
/** handler跟HandlerThread结合使用的测试方法*/public void decreaseClick(View view){Logger.d();secondHandler.getSerialThread().post(new Runnable() {@Overridepublic void run() {Logger.d("SecondHandler ThreadId = " + Thread.currentThread().getId());int sum = decrease(300, 180);try {Thread.sleep(8 * 1000); //模拟减法运算是一个非常复杂的运算,所以要开线程} catch (InterruptedException e) {e.printStackTrace();}result = "result2 = " + sum;Message message = new Message();message.what = SecondHandler.UI_REFLESH;message.obj = result;handler.sendMessage(message); //通过主线程更新UI}});}//减法运算private int decrease(int a, int b){return a - b;}
首先通过 getSerialThread()方法获取secondHandler对象,然后调用了post方法,在run方法中执行了减法decrease(300, 180)运算,减法运算结束后会调用一个休眠函数Thread.sleep(8 * 1000),休眠8秒来模拟是耗时操作,休眠结束后会通过主线程的handler来通知界面更新减法的结果。运行结果如下:
代码参考:https://github.com/gunder1129/android-tool/commit/219738d73f22763ab531800e423a66c8d3e72860
参考博客:https://blog.csdn.net/weixin_41101173/article/details/79687313
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