Handler，MessageQueue Loop 和Message的原理解析

先介绍和handler一起工作的几个组件

Handler的方法介绍

代码示例

package liu.peng.weather;

import java.util.Timer;
import java.util.TimerTask;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.ActionBarActivity;
import android.widget.ImageView;

public class MainActivity extends ActionBarActivity {
    private int imageIds[] = new int[]{R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,
            R.drawable.ic_launcher,R.drawable.ic_launcher};
    private int currentId = 0;
    ImageView image;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        image = (ImageView)findViewById(R.id.image);
        final Handler myHandler = new Handler(){
            @Override
            public void handleMessage(Message msg) {
                if (msg.what == 0x123) {
                    image.setImageResource(imageIds[currentId++%imageIds.length]);
                }
            }
        };
        new Timer().schedule(new TimerTask() {

            @Override
            public void run() {
                myHandler.sendEmptyMessage(0x123);
            }
        }, 0,1200);
    }
}

另外一个代码示例

package liu.peng.weather;

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

import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {
    static final String UPPER_NUM = "upper";
    EditText edit;
    CalThread calThread;
    class CalThread extends Thread{
        public Handler myHandler;
        @Override
            public void run() {
                Looper.prepare();
                myHandler = new Handler(){
                    public void handleMessage(android.os.Message msg) {
                        if (msg.what == 0x123) {
                            int upper = msg.getData().getInt(UPPER_NUM);
                            List<Integer> nums = new ArrayList<Integer>();
                            outer:
                                for(int i = 2;i<=upper;i++){
                                    for(int j = 2;j<=Math.sqrt(i);j++){
                                        if (i != 2 && i%j == 0) {
                                            continue outer;
                                        }
                                    }
                                    nums.add(i);
                                }
                            Toast.makeText(MainActivity.this, nums.toString(), Toast.LENGTH_LONG).show();
                        }
                    };
                };
                Looper.loop();
            }
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        edit = (EditText)findViewById(R.id.edit);
        calThread.start();

    }
    public void cal(View source){
        Message msg = new Message();
        msg.what = 0x123;
        Bundle bundle = new Bundle();
        bundle.putInt(UPPER_NUM,Integer.parseInt(edit.getText().toString()));
        msg.setData(bundle);
        calThread.myHandler.sendMessage(msg);
    }
}