Activity与Activity间的通信

雨点打透心脏的1/2处 2022-08-22 01:24 216阅读 0赞

## 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);
        }
    
    
    }

--------------------

参考《Android编程权威指南》