android-Handler机制总结完整版

android:Handler整理总结当我们在处理下载或是其他需要长时间执行的任务时，如果直接把处理函数放Activity的OnCreate或是OnStart中，会导致执行过程中整个Activity无响应，如果时间过长，程序还会挂掉。Handler就是把这些功能放到一个单独的线程里执行，与Activity互不影响。我们简单用例子来说明：小实例一：5秒钟更新一下Title（标题），如图：代码如下：viewplaincopytoclipboardprint?packagecom.android.tutor;importjava.util.Timer;importjava.util.TimerTask;importandroid.app.Activity;importandroid.os.Bundle;importandroid.os.Handler;importandroid.os.Message;publicclassHandlerDemoextendsActivity{//title为setTitle方法提供变量,这里为了方便我设置成了int型privateinttitle=0;privateHandlermHandler=newHandler(){publicvoidhandleMessage(Messagemsg){switch(msg.what){case1:updateTitle();break;}};};publicvoidonCreate(BundlesavedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);Timertimer=newTimer();timer.scheduleAtFixedRate(newMyTask(),1,5000);}privateclassMyTaskextendsTimerTask{@Overridepublicvoidrun(){Messagemessage=newMessage();message.what=1;mHandler.sendMessage(message);}}publicvoidupdateTitle(){setTitle("WelcometoMrWei'sblog"+title);title++;}}packagecom.android.tutor;importjava.util.Timer;importjava.util.TimerTask;importandroid.app.Activity;importandroid.os.Bundle;importandroid.os.Handler;importandroid.os.Message;publicclassHandlerDemoextendsActivity{ //title为setTitle方法提供变量,这里为了方便我设置成了int型 privateinttitle=0; privateHandlermHandler=newHandler(){ publicvoidhandleMessage(Messagemsg){ switch(msg.what){ case1: updateTitle(); break; } }; }; publicvoidonCreate(BundlesavedInstanceState){ super.onCreate(savedInstanceState); setContentView(R.layout.main); Timertimer=newTimer(); timer.scheduleAtFixedRate(newMyTask(),1,5000); } privateclassMyTaskextendsTimerTask{ @Override publicvoidrun(){ Messagemessage=newMessage(); message.what=1; mHandler.sendMessage(message); } } publicvoidupdateTitle(){ setTitle("WelcometoMrWei'sblog"+title); title++; }}小实例二：用Handler更新进度条ProgressBar；如图：当按开始按钮时，进度条会每隔500毫秒加1,直到加到100或者按停止时停止代码：viewplaincopytoclipboardprint?importandroid.app.Activity;importandroid.os.Bundle;importandroid.os.Handler;importandroid.view.View;importandroid.view.View.OnClickListener;importandroid.widget.Button;importandroid.widget.ProgressBar;publicclassmainextendsActivity{/**Calledwhentheactivityisfirstcreated.*/ProgressBarpb1;Handlerhandle=newHandler();//新建一个Handler对象Buttonb1;Buttonb2;@OverridepublicvoidonCreate(BundlesavedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);pb1=(ProgressBar)findViewById(R.id.pb1);pb1.setProgress(0);b1=(Button)findViewById(R.id.b1);b1.setOnClickListener(b1Lis);b2=(Button)findViewById(R.id.b2);b2.setOnClickListener(b2Lis);}privateOnClickListenerb1Lis=newOnClickListener(){@OverridepublicvoidonClick(Viewv){//TODOAuto-generatedmethodstubhandle.post(add);//开始执行add}};privateOnClickListenerb2Lis=newOnClickListener(){@OverridepublicvoidonClick(Viewv){//TODOAuto-generatedmethodstubhandle.removeCallbacks(add);//停止执行pb1.setProgress(0);}};intpro=0;Runnableadd=newRunnable(){//定义add@Overridepublicvoidrun(){//TODOAuto-generatedmethodstubpro=pb1.getProgress()+1;pb1.setProgress(pro);setTitle(String.valueOf(pro));if(pro<100){handle.postDelayed(add,500);//如果进度小于100,，则延迟500毫秒后重复执行add}}};}importandroid.app.Activity;importandroid.os.Bundle;importandroid.os.Handler;importandroid.view.View;importandroid.view.View.OnClickListener;importandroid.widget.Button;importandroid.widget.ProgressBar;publicclassmainextendsActivity{ /**Calledwhentheactivityisfirstcreated.*/ ProgressBarpb1; Handlerhandle=newHandler(); //新建一个Handler对象 Buttonb1; Buttonb2; @Override publicvoidonCreate(BundlesavedInstanceState){ super.onCreate(savedInstanceState); setContentView(R.layout.main); pb1=(ProgressBar)findViewById(R.id.pb1); pb1.setProgress(0); b1=(Button)findViewById(R.id.b1); b1.setOnClickListener(b1Lis); b2=(Button)findViewById(R.id.b2); b2.setOnClickListener(b2Lis); } privateOnClickListenerb1Lis=newOnClickListener(){ @Override publicvoidonClick(Viewv){ //TODOAuto-generatedmethodstub handle.post(add); //开始执行add } }; privateOnClickListenerb2Lis=newOnClickListener(){ @Override publicvoidonClick(Viewv){ //TODOAuto-generatedmethodstub handle.removeCallbacks(add); //停止执行 pb1.setProgress(0); } }; intpro=0; Runnable