Android基础2

Activity的使用

MainActivity.java

package a.b.c.myapplication;

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

import androidx.activity.EdgeToEdge;
import androidx.activity.result.ActivityResult;
import androidx.activity.result.ActivityResultCallback;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContract;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;

public class MainActivity extends AppCompatActivity
{
    Button btn_start,btn_startForResult;
    String logtag="hyqhyqhyq";
//老方法，通过复写onActivityResult函数来接受返回结构
//    @Override
//    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data)
//    {
//        super.onActivityResult(requestCode, resultCode, data);
//
//        if(data == null)
//        {
//            return;
//        }
//        if(resultCode == requestCode && requestCode == 234)
//        {
//            String ret = data.getStringExtra("key1");
//            Log.i("This is ret",ret);
//        }
//    }
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });
        btn_start = findViewById(R.id.btn_startActivity);
        btn_start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view)
            {
                Intent intent = new Intent(MainActivity.this, SubActivity02.class);//第一个参数：谁下发的命令，第二个参数：打开哪个Activity
                startActivity(intent);
            }
        });
        // 新方法接受返回结果
        ActivityResultLauncher launcher = registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), new ActivityResultCallback<ActivityResult>() {
            @Override
            public void onActivityResult(ActivityResult result)
            {
                Log.i(logtag,result.getData().getStringExtra("key1"));
            }
        });
        btn_startForResult = findViewById(R.id.btn_startActivityGetResult);
        btn_startForResult.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view)
            {
                Intent intent = new Intent(MainActivity.this,SubActivity03.class);
//                startActivityForResult(intent,234);
                launcher.launch(intent);
            }
        });
        
    }
}
/*ActivityResultLauncher 和 registerForActivityResult:

ActivityResultLauncher 是一个接口，用于启动目标活动并接收其结果。
registerForActivityResult 是一个新的方法，用于注册一个能够处理特定结果的 ActivityResultLauncher 实例。它接受两个参数：
第一个参数是一个 ActivityResultContract 的实例，用于指定要执行的操作类型。在这里使用的是 ActivityResultContracts.StartActivityForResult()，表示注册一个能够处理 startActivityForResult 操作的 launcher。
第二个参数是一个 ActivityResultCallback<ActivityResult> 的实例，用于处理从目标活动返回的结果。
onActivityResult 方法:

这是注册的 ActivityResultCallback 的实现部分。
当目标活动返回结果时，系统将调用 onActivityResult 方法，并传递一个 ActivityResult 对象作为参数。
在这里，通过 result.getData().getStringExtra("key1") 获取从目标活动返回的数据中名为 "key1" 的字符串数据，并将其记录到日志中。
Log.i(logtag, ...):

Log.i 是 Android 提供的日志输出方法，用于记录信息级别的日志。
logtag 应该是一个字符串常量，用于标识日志的来源或者类别。*/

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <Button
            android:id="@+id/btn_startActivity"
            android:text="启动Activity"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
        <Button
            android:id="@+id/btn_startActivityGetResult"
            android:text="启动Activity并获取返回结果"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
    </LinearLayout>
</LinearLayout>

SubActivity02.java

package a.b.c.myapplication;

import android.os.Bundle;
import android.util.Log;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

public class SubActivity02 extends AppCompatActivity
{

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState)
    {
        setContentView(R.layout.activity_sub02);
        super.onCreate(savedInstanceState);
        Log.i("This is SubActivity02","SubActivity02 onCreate");
    }
}

activity_sub02.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <TextView
        android:gravity="center"
        android:textSize="40dp"
        android:text="我是第二个Activity"
        android:layout_width="match_parent"
        android:layout_height="50dp"/>
</LinearLayout>

SubActivity03.java

package a.b.c.myapplication;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import androidx.annotation.Nullable;

public class SubActivity03 extends Activity
{
    TextView tv;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sub03);
        tv = findViewById(R.id.tv_setResult);
        tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view)
            {
                Intent intent = new Intent();
                intent.setClass(SubActivity03.this,MainActivity.class);
                intent.putExtra("key1","这是结果1,来自SubActivity03");
                setResult(234,intent);
                SubActivity03.this.finish();
            }
        });
    }
}

activity_sub03.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <TextView
        android:gravity="center"
        android:textSize="40dp"
        android:text="我是第三个Activity"
        android:id="@+id/tv_setResult"
        android:layout_width="match_parent"
        android:layout_height="50dp"/>
</LinearLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <TextView
        android:gravity="center"
        android:textSize="40dp"
        android:text="我是第三个Activity"
        android:id="@+id/tv_setResult"
        android:layout_width="match_parent"
        android:layout_height="50dp"/>
</LinearLayout>

Service介绍

Service是android系统的四大组件之一，是一种长生命周期的，没有可视化界面，运行于后台的一种服务程序

启动方式

(1)Started Service被开启的service通过其他组件调用startService()被创建，这种service可以无限地运行下去，必须调用stopSelf()方法或者其他组件调用stopService()来停止它，当service被停止时，系统会销毁它

在清单文件中注册Service

<service android:name=".service.MyService01"></service>

MainActivity.java

btn_startService = findViewById(R.id.btn_startService);
        btn_startService.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view)
            {
                Intent intent = new Intent(MainActivity.this, MyService01.class);
                startService(intent);
            }
        });
        btn_stopService = findViewById(R.id.btn_stopService);
        btn_stopService.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view)
            {
                Intent intent = new Intent(MainActivity.this, MyService01.class);
                stopService(intent);
            }
        });

activity_main.xml

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    >
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btn_startService"
        android:text="启动Service"
        />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btn_stopService"
        android:text="停止Service"
        />
</LinearLayout>

(2)Bounded Service被绑定地service是当其他组件(一个客户)调用bindService()来创建的，客户可以通过一个IBinder接口和service进行通信，客户可以通过unbindService()方法来关闭这种连接，一个service可以同时和多个客户绑定，当多个客户都解除绑定之后，系统会销毁service

在清单文件中注册Service

<service android:name=".service.MyBindService"></service>

MainActivity.java

注意：复制粘贴时，启动哪个activity要注意，这里卡了好久

btn_binService = findViewById(R.id.btn_bindService);
   btn_binService.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View view)
       {
           Intent intent = new Intent(MainActivity.this,MyBindService.class);
           bindService(intent,conn, 0);
       }
   });
   btn_unBindService = findViewById(R.id.btn_unbindService);
   btn_unBindService.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View view)
       {
           Intent intent = new Intent(MainActivity.this, MyBindeService.class);
           try
           {
               unbindService(conn);
           }
           catch (Exception e)
           {
               e.printStackTrace();
           }
       }
   });

MyBinderService.java

package a.b.c.myapplication.service;

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;

import androidx.annotation.Nullable;

public class MyBindService extends Service
{
    private MyBinder binder = new MyBinder();

    String logTag = "MyBinderService";
    public class MyBinder extends Binder
    {
        public MyBinder()
        {
            Log.i(logTag,"in MyBinder");
        }

        public MyBindService getService()
        {
            return MyBindService.this;
        }
    }

    @Override
    public void onCreate()
    {
        super.onCreate();
    }

    @Override
    public void onDestroy()
    {
        super.onDestroy();
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent)
    {
        return binder;
    }

    @Override
    public boolean onUnbind(Intent intent)
    {
        Log.i(logTag, "onUnbind");
        return super.onUnbind(intent);
    }
}

BroadcastReceiver介绍

BroadcastReceiver(广播接受器)是Android系统的四大组件之一，用于监听 / 接受 应用发出的广播消息，并做出响应

应用场景：不同组件之间通信(包括应用内 / 不同应用之间)；与Android系统在特定情况下的通信(如电话呼入时、网络可用时)；多线程通信

Android广播分为两个角色：广播发送者、广播接受者

实现原理

(Android中的广播使用了设计模式中的观察者模式)：基于消息的发布/订阅事件模型

模型中有3个角色：

消息订阅者(广播接受者)/消息发布者(广播发布者)/消息中心(AMS，即Activity Manager Service)

广播接收者通过Binder机制在AMS注册

广播发送者通过Binder机制向AMS发送广播

AMS根据广播发送者要求，在已注册列表中，寻找合适的广播接收者(寻找依据：IntentFilter/Permission)

AMS将广播发送到合适的广播接收者相应的消息循环队列中

注册的方式分为两种：静态注册、动态注册

(1)静态注册

在AndroidManifest.xml里面通过标签声明，当此App首次启动时，系统会自动实例化mBroadReceive类，并注册到系统中，静态注册是常驻广播，不受任何组件生命周期的影响

<receiver android:name=".MyReceiver.MyReceiver"
            android:exported="false">//android:exported="false" 指定了该接收器是否能被其他应用组件调用或者是从外部调用。false 表示这个接收器仅对自己的应用可见，其他应用无法直接调用它。
            <intent-filter>
                <action android:name="golvRuleaaa">//<intent-filter> 标签定义了接收器可以处理的广播意图（Intent）过滤器。<action> 标签用于指定接收器要处理的广播动作（Action）。在这个例子中，动作名称是 "golvRuleaaa"。这表示接收器只会对发送这个特定动作的广播进行处理。
                </action>
            </intent-filter>
        </receiver

(2)动态注册

在代码中通过调用Context的regisertReceiver()方法进行动态注册BroadReceiver，注册广播后，要在相应位置记得销毁广播，即在onPause()中unregisertReceiver(mBroadcastReceiver)，当此Activity实例化时，会动态将MyBroadcastReceiver注册到系统中，当此Activity销毁时，动态注册的MyBroadReceiver将不再接受到相应的广播

注意：动态广播最好在Activity中的onResume()注册、onPause注销。

原因：

对于动态广播，有注册就必然得有注销，否则会导致内存泄露

重复注册、重复注销也不允许

动态注册是非常驻广播，灵活，跟随组件的生命周期变化

在AndroidManifest.xml中注册，并设置优先级(静态注册)

<receiver android:name=".MyReceiver.OrderReceiver01"
    android:exported="false">
    <intent-filter android:priority="1000">
        <action android:name="golvRuleaaa">
        </action>
    </intent-filter>
</receiver>
<receiver android:name=".MyReceiver.OrderReceiver02"
    android:exported="false">
    <intent-filter android:priority="500">
        <action android:name="golvRuleaaa">
        </action>
    </intent-filter>
</receiver>
<receiver android:name=".MyReceiver.OrderReceiver03"
    android:exported="false">
    <intent-filter android:priority="200">
        <action android:name="golvRuleaaa">
        </action>
    </intent-filter>
</receiver>

在MainActivity中动态注册

OrderReceiver01 orderReceiver01 = new OrderReceiver01();
OrderReceiver02 orderReceiver02 = new OrderReceiver02();
OrderReceiver03 orderReceiver03 = new OrderReceiver03();
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("golvRuleaaa");
registerReceiver(orderReceiver01, intentFilter);
registerReceiver(orderReceiver02,intentFilter);
registerReceiver(orderReceiver03,intentFilter);

MainActivity.java(包括了无序广播和有效广播)

btn_sendBroadcast = findViewById(R.id.btn_broadcast);
        btn_sendBroadcast.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view)
            {
                Intent intetnt = new Intent(MainActivity.this, MyReceiver.class);
                intetnt.setAction("guolvRuleaaa");
                intetnt.putExtra("key2","这是无序广播内容1");
                sendBroadcast(intetnt);
            }
        });

        OrderReceiver01 orderReceiver01 = new OrderReceiver01();
        OrderReceiver02 orderReceiver02 = new OrderReceiver02();
        OrderReceiver03 orderReceiver03 = new OrderReceiver03();
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction("guolvRuleaaa");
        registerReceiver(orderReceiver01, intentFilter);
        registerReceiver(orderReceiver02,intentFilter);
        registerReceiver(orderReceiver03,intentFilter);

        btn_orderBroadcast = findViewById(R.id.btn_orderBroadcast);
        btn_orderBroadcast.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view)
            {
                Intent intent = new Intent();
                intent.setAction("guolvRuleaaa");
                String data = "这是原始数据";
                Bundle extData = new Bundle();

                sendOrderedBroadcast(intent,null,new MyReceiver(),null,0,data,extData);
            }
        });

MyReceiver.java

package a.b.c.myapplication.MyReceiver;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;

public class MyReceiver extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context, Intent intent)
    {
        String action = intent.getAction();
        if(action.equals("guolvRuleaaa"))
        {
            //Log.i("MyReceiver",intent.getStringExtra("key2"));
            String data = getResultData();
            Log.i("OrderReceiver01","接受到内容,"+data);
        }
    }
}

OrderReceiver01.java

package a.b.c.myapplication.MyReceiver;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;

public class OrderReceiver01 extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context, Intent intent)
    {
        String action = intent.getAction();
        if(action.equals("guolvRuleaaa"))
        {
            String data = getResultData();
            Log.i("OrderReceiver01","接受到内容,"+data);
            setResultData("内容已经被修改OrderReceive01修改");
            //Log.i("OrderReceiver01",intent.getStringExtra("key2"));
        }

    }
}

OrderReceiver02.java

package a.b.c.myapplication.MyReceiver;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;

public class OrderReceiver02 extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context, Intent intent)
    {
        String action = intent.getAction();
        if(action.equals("guolvRuleaaa"))
        {
            String data = getResultData();
            Log.i("OrderReceiver02","接受到内容,"+data);
            setResultData("内容已经被修改OrderReceive02修改");
            //Log.i("OrderReceiver01",intent.getStringExtra("key2"));
        }

    }
}

OrderReceiver03.java

package a.b.c.myapplication.MyReceiver;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;

public class OrderReceiver03 extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context, Intent intent)
    {
        String action = intent.getAction();
        if(action.equals("guolvRuleaaa"))
        {
            String data = getResultData();
            Log.i("OrderReceiver03","接受到内容,"+data);
            setResultData("内容已经被修改OrderReceive03修改");
            //Log.i("OrderReceiver01",intent.getStringExtra("key2"));
        }

    }
}