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

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

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);

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);
}

}

参考《Android编程权威指南》