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resultCodesetResult(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requestCoderesultCode就是在Demo2_1Acitvity中setResult(int, Intent);传入的int resultCodedata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);    }}

---

参考《Android编程权威指南》