19 Handler 子线程向主线程发送信息

时间：2020-12-13 05:58:23
  • 案例一 Message创建三种方法:
package com.example.day19_handler_demo1;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.app.Activity;

import android.util.Log;

import android.view.Menu;

import android.widget.TextView;

public class MainActivity extends Activity {

    private TextView tv;

    private int count =0;

    private Handler handler = new Handler(){

        public void handleMessage(android.os.Message msg) {

            Log.e("AAA", "=handleMessage=>"+Thread.currentThread().getName());

            //处理消息

            //获取消息

            int num = msg.arg1;

            //更新数据

            tv.setText(num+"");

        };

    };

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        tv = (TextView) findViewById(R.id.tv);

//       android.view.ViewRootImpl$CalledFromWrongThreadException:

//           Only the original thread that created a view hierarchy

//           can touch its views.

        new Thread(){

            public void run() {

                while(true){

                    if(count<100){

                        count++;

                    }

                    Log.e("AAA", "=Thread=>"+Thread.currentThread().getName());

                //  tv.setText(count+"");

                    //方式一获取Message对象  不建议使用

                    //Message msg = new Message(); 如果用sendToTarget想要setTarget

                    //方式二获取Message对象

                    //Message msg = Message.obtain(); 方便后面用sendToTarget

                    //方式三获取Message对象

                    Message msg = handler.obtainMessage();

                    //msg携带数据

                    msg.arg1 = count;

                    //使用Handler发送数据

                    handler.sendMessage(msg);

                    try {

                        sleep(1000);

                    } catch (InterruptedException e) {

                        // TODO Auto-generated catch block

                        e.printStackTrace();

                    }

                }

            };

        }.start();

    }

}
  • 案例二 Message几个信息载体:
package com.qf.day19_handler_demo2;

import android.app.Activity;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.util.Log;

import android.view.View;

public class MainActivity extends Activity {

    private Handler handler = new Handler(){

        public void handleMessage(android.os.Message msg) {

            //接收和处理消息的

            switch (msg.what) {//根据标记进行处理数据

            case 1:

                int a = msg.arg1;

                int a2 = msg.arg2;

                String str = (String) msg.obj;

                int flag = msg.what;

                Log.e("AAA", "==a=="+a);

                Log.e("AAA", "==a2=="+a2);

                Log.e("AAA", "==str=="+str);

                Log.e("AAA", "==flag=="+flag);

                break;

            case 2:

                Log.e("AAAA", "AAAAAAAAAAAAAAAA");

                break;

            default:

                break;

            }

        };

    };

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

    }

    //子线程里的数据发送到主线程

    public void OnMyClick(View v){

        new Thread(){

            public void run() {

                //获取消息的载体对象

                Message msg = Message.obtain();

                msg.arg1 = 100;

                msg.arg2 = 200;//arg1,arg2:都是int类型数据

                msg.obj = "我是大数据"; //Object对象   string   Bitmap   List<T>

                msg.what = 1;//int 类型   标记

                handler.sendMessage(msg);

            };

        }.start();

    }

}
  • 案例三 几个发送msg的方式:
package com.qf.day19_handler_demo4;

import android.app.Activity;

import android.app.ProgressDialog;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.util.Log;

import android.view.View;

import android.widget.ImageView;

public class MainActivity extends Activity {

    private ImageView ivShow;

    Handler handler = new Handler();

    Handler handler2 = new Handler(){

        public void handleMessage(android.os.Message msg) {

            switch (msg.what) {

            case 1:

                pDialog.show();

                break;

            case 2:

                Bitmap bitmap = (Bitmap) msg.obj;

                ivShow.setImageBitmap(bitmap);

                pDialog.dismiss();

                break;

            default:

                break;

            }

        };

    };

    private ProgressDialog pDialog;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        ivShow = (ImageView) findViewById(R.id.iv_show);

        pDialog = new ProgressDialog(MainActivity.this);

        pDialog.setTitle("下载图片");

        pDialog.setIcon(R.drawable.ic_launcher);

        pDialog.setMessage("正在下载中,请稍后...");

    }

    public void MyLoadClick(View v) {

        //pDialog.show();

        //开启子线程下载图片

        new Thread(){

            public void run() {

                //在子线程展示

                //发送null消息  只设置一个标记

                handler2.sendEmptyMessage(1);

                byte[] data = HttpUtil.getHttpResult("https://ss2.baidu.com/6ONYsjip0QIZ8tyhnq/it/u=2507878052,3446525205&fm=58");

                final Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);

                //第一种方式   将代码块发送到主线程 在内部直接一个匿名内部类runnable 可以直接更新UI（主线程）

//              handler.post(new Runnable() {

//

//                  @Override

//                  public void run() {

//                      // TODO Auto-generated method stub

//                      Log.e("AAA", "=handler=>"+Thread.currentThread().getName());

//

//                      //更新Ui

//                      ivShow.setImageBitmap(bitmap);

//                      pDialog.dismiss();

//                  }

//              });

                //延迟发送 在内部直接一个匿名内部类runnable 可以直接更新UI（主线程）

//              handler.postDelayed(r, delayMillis)

                //第二种方式     使用msg  携带数据到主线程

//              Message msg = Message.obtain();

//              msg.obj = bitmap;

//              msg.what = 2;

//              handler2.sendMessage(msg);

//              延迟发送一个msg

                //handler2.sendMessageDelayed(msg, delayMillis)

                //第三种   sendToTarget  发送到那个Handler

//              Message msg = handler2.obtainMessage();

//              msg.obj = bitmap;

//              msg.what = 2;

//              msg.sendToTarget();//发送给那个Handler

                //第四种方式

                Message msg = Message.obtain();

                msg.obj = bitmap;

                msg.what = 2;

                msg.setTarget(handler2);//指明是那个Handler

                msg.sendToTarget();//发送给那个Handler

            };

        }.start();

    }

}

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