Activity与Activity间的通信

Activity与Activity间的通信

Activity的启动

一个Activity启动另一个Activity最简单的方法就是用startActivity(Intent intent)方法,这个方法调用请求是发送给操作系统的ActivityManager负责创建Activity实例并调用其onCreat()方法。ActivityManager是通过传入startActivity(Intent intent)方法的Intent参数知道需要启动哪一个Activity。

ActivityManager维护着一个非特定应用独享的回退栈。所有应用的activity都共享该回退栈。这也是将ActivityManager设计成操作系统级的activity管理器来负责启动应用activity的原因之一。不局限与单个应用，回退栈作为一个整体共享给操作系统及设备使用。

描述：通过 Demo2Activity 启动 Demo2_1Activity 或 Demo2_2Activity，Demo2_1Activity或Demo2_2Activity退出后把信息回馈到 Demo2Activity

1. 在Demo2Activity中

   Intent intent = new Intent(Demo2Activity.this, Demo2_1Activity.class);
   intent.putExtra("Demo2Activity", "Hello,Demo2_1Acitvity,this is Demo2Activity");
   startActivityForResult(intent, 0);
   //requestCode必须大于等于0，否则onActivityResult()方法不会执行
   //如果在Demo2_1Acitvity中没有返回消息，那么resultCode会等于requestCode，并且data = null
   

   这样，就把消息传递给了Demo2_1Acitvity

2. 在Demo2_1Acitvity中

   /*收到 Demo2Activity 的消息*/
   Intent intent1 = getIntent();
   Log.d("demoinfo", "Demo2_1Activity收到：  " + intent1.getStringExtra("Demo2Activity"));
   
   /*给Demo2Activity发送消息*/
   Intent intent2 = new Intent();
   intent2.putExtra("Demo2_1Activity", "I‘m Demo2_1Activity!!");
   //setResult(1); 两种方式，这个是只传一个resultCode
   setResult(1, intent2);
   

3. 在Demo2Activity中重载onActivityResult(int requestCode, int resultCode, Intent data)方法

   requestCode就是之前在Demo2Activity中startActivityForResult(Intent, int)传入的requestCode
   resultCode就是在Demo2_1Acitvity中setResult(int, Intent);传入的int resultCode
   data就是在Demo2_1Acitvity中setResult(int, Intent);传入的Intent
   

代码：

package com.ashzheng.studydemo.demo2;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.ashzheng.studydemo.R;

public class Demo2Activity extends Activity {

    private Button bt1;
    private Button bt2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_demo2);

        bt1 = (Button) findViewById(R.id.demo2_bt1);
        bt2 = (Button) findViewById(R.id.demo2_bt2);

        bt1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(Demo2Activity.this, Demo2_1Activity.class);
                intent.putExtra("Demo2Activity", "Hello,Demo2_1Acitvity,this is Demo2Activity");
//                startActivity(intent);
                startActivityForResult(intent, 0);//requestCode必须大于等于0，否则onActivityResult()方法不会执行
            }
        });

        bt2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(Demo2Activity.this, Demo2_2Activity.class);
                intent.putExtra("Demo2Activity", "Hello,Demo2_2Acitvity,this is Demo2Activity");
//                startActivity(intent);
                startActivityForResult(intent, 0);//requestCode必须大于等于0，否则onActivityResult()方法不会执行
            }
        });

    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        Log.d("demoinfo", "requestCode = " + requestCode);
        Log.d("demoinfo", "resultCode = " + resultCode);
        if(null == data){
            Log.d("demoinfo", "data == null");
            return;
        }

        switch (resultCode){
            case 1:
                Log.d("demoinfo", data.getStringExtra("Demo2_1Activity"));
                break;
            case 2:
                Log.d("demoinfo", data.getStringExtra("Demo2_2Activity"));
                break;
        }

    }
}

package com.ashzheng.studydemo.demo2;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;

import com.ashzheng.studydemo.R;

public class Demo2_1Activity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_demo2_1);

        Intent intent1 = getIntent();
        Log.d("demoinfo", "Demo2_1Activity收到：  " + intent1.getStringExtra("Demo2Activity"));

        Intent intent2 = new Intent();
        intent2.putExtra("Demo2_1Activity", "I‘m Demo2_1Activity!!");
        //setResult(1);
        setResult(1, intent2);

    }

}

package com.ashzheng.studydemo.demo2;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;

import com.ashzheng.studydemo.R;

public class Demo2_2Activity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_demo2_2);

        Intent intent1 = getIntent();
        Log.d("demoinfo", "Demo2_2Activity收到：  " + intent1.getStringExtra("Demo2Activity"));

        Intent intent2 = new Intent();
        intent2.putExtra("Demo2_2Activity", "I‘m Demo2_2Activity!!");
        //setResult(2);
        setResult(2, intent2);
    }

}