<Handler>练习

package com.crazyit.handlerdemo;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

/**
* Handler 工作原理
*/
public class HandlerTestActivity extends Activity {

public static final String UPPER_NUM = "upper";
EditText input_num;
Button btn;
NewThread newThread;

class NewThread extends Thread {
public Handler mHandelr;

@Override
public void run() {
Looper.prepare();  //创建当前线程的 Looper对象
mHandelr = new Handler() {//创建 Handler() 子类 然后重写 handleMessage() 方法

@Override
public void handleMessage(Message msg) {
if (msg.what == 0x123) {
int upper = msg.getData().getInt(UPPER_NUM);

List<Integer> nums = new ArrayList<Integer>();
//计算 从2开始 到upper的所有质数
outer:
for (int i = 2; i <= upper; i++) {

//用i除以从2开始, 到i的平方根的所有数
for (int j = 2; j <= Math.sqrt(i); j++) {

//如果可以整除,则表明这个数不是质数 就跳过
if (i != 2 && i % j == 0) {
continue outer; //就跳过
}
}
nums.add(i);
}
Toast.makeText(HandlerTestActivity.this, nums.toString(), Toast.LENGTH_LONG).show();
}
}
};

Looper.loop();  //最后调用Looper的 loop( )方法,启动Looper
}
}

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_handler_test);

input_num = (EditText) findViewById(R.id.et_num);
newThread = new NewThread();
//启动线程
newThread.start();
}

//为按钮的点击事件绑定处理事件
public void jiSuan(View view) {
//创建消息
Message msg = new Message();
msg.what = 0x123;
Bundle bundle = new Bundle();
bundle.putInt(UPPER_NUM, Integer.parseInt(input_num.getText().toString().trim()));

msg.setData(bundle);
//向子线程中的 Handler 发送消息
newThread.mHandelr.sendMessage(msg);

}

}

布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.crazyit.handlerdemo.HandlerTestActivity">

<EditText
android:id="@+id/et_num"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="请输入数字"
android:inputType="number" />

<Button
android:id="@+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="jiSuan"
android:text="计算" />

</LinearLayout>