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Android入门之BroadCast模拟实现异地登录事件发生后的主动退出

TGITCIC 人气:0

简介

随着对BroadCast的越来越深入,我们今天要实现一个稍微复杂一点的BroadCast。即我们常用来有时APP打开时如果多个设备同时登录一个帐号,而我们只允许一个设备登录一个帐号时,此时我们的APP会弹一个对话框如:您的账号在别处登录,请重新登陆!。

设计

要制作这样的效果我们依旧是采用BroadCast,而且是一个自定义的Broadcast。此处需要:

1.自定义send一个broadcast;

2.注册一个receiver,使得它监听我们这个自定义的broadcast;

3.在receiver的onReceive事件中,弹出一个“无窗体悬浮alert dialog”;

4.由于Android6及以后的相应权限问题,你还要添加这个无窗体的悬浮alert dialog的权限;

5.又由于我们用的是SDK27及以后版本,因此光添加权限还没有用,还要使用代码唤出android关于这个app的一个“授权”系统窗口,在这个授权窗口内,用户自己点:allow后再进行打开这个app操作,此时这个悬浮alert dialog才能正确被唤起否则当这个alert dialog一旦被唤出你会得到一个permission denied 2038的错误,然后Android App自动退出;

好了,说了这么多我们来看代码

全代码

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
 
    <Button
        android:id="@+id/buttonLoginInOtherPlace"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="模拟异地登录" />
</LinearLayout>

activity_login.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
 
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
 
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="login_id:" />
 
        <EditText
            android:width="120dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </LinearLayout>
 
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
 
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="password:" />
 
        <EditText
            android:width="120dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </LinearLayout>
 
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">
 
        <Button
            android:id="@+id/buttonLoginSubmit"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="点一下代表登录了" />
    </LinearLayout>
</LinearLayout>

以上定义了两个窗体,运行顺序如下:

先来看我们的Receiver,它接受来自activity_main的【模拟异地登录】按钮发送过来的broad cast。

BroadCastReceiver.java

package org.mk.android.demo.broadcast;
 
import android.app.AlertDialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.graphics.PixelFormat;
import android.os.Build;
import android.provider.Settings;
import android.util.Log;
import android.view.Window;
import android.view.WindowManager;
 
public class BroadCastReceiver extends BroadcastReceiver {
    private final String TAG = "BroadCastWithActivity";
 
    @Override
    public void onReceive(final Context context, Intent intent) {
 
        Log.i(TAG, "receive broadcast->" + intent.getAction());
        AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(context);
        dialogBuilder.setTitle("警告:");
        dialogBuilder.setMessage("您的账号在别处登录,请重新登陆!");
        dialogBuilder.setCancelable(false);
        dialogBuilder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                ActivityCollector.getInstance().finishAll();
                Intent intent = new Intent(context, LoginActivity.class);
                intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                context.startActivity(intent);
            }
        });
        AlertDialog alertDialog = dialogBuilder.create();
        alertDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY);
        alertDialog.show();
    }
}

接着,我们来看AndroidManifest.xml文件中的注册以及相应的静态权限申请(这个对话框除了静态权限还需要代码在弹出对话框前申请动态权限,这块代码我们写在了MainActivity.java里的)。

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">
    <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
    <uses-permission android:name="android.permission.SYSTEM_OVERLAY_WINDOW" />
    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.DemoBroadCastWithActivity"
        tools:targetApi="31">
        <activity
            android:name=".LoginActivity"
            android:exported="false">
            <meta-data
                android:name="android.app.lib_name"
                android:value="" />
        </activity>
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
 
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
 
            <meta-data
                android:name="android.app.lib_name"
                android:value="" />
        </activity>
        <receiver android:name=".BroadCastReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED"/>
            </intent-filter>
            <intent-filter>
                <action android:name="ANDROID.INTENT.ACTION.MEDIA_MOUNTED"/>
                <action android:name="ANDROID.INTENT.ACTION.MEDIA_UNMOUNTED"/>
                <data android:scheme="file"/>
            </intent-filter>
        </receiver>
    </application>
 
</manifest>

接着我们来看我们的BroadCastReceiver写法。

BroadCastReceiver.java

package org.mk.android.demo.broadcast;
 
import android.app.AlertDialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.graphics.PixelFormat;
import android.os.Build;
import android.provider.Settings;
import android.util.Log;
import android.view.Window;
import android.view.WindowManager;
 
public class BroadCastReceiver extends BroadcastReceiver {
    private final String TAG = "BroadCastWithActivity";
    private static final String BROADCAST_ACTON = "org.mk.android.demo.broadcast";
    @Override
    public void onReceive(final Context context, Intent intent) {
        if(intent.getAction().equals(BROADCAST_ACTON)) {
            Log.i(TAG, "receive broadcast->" + intent.getAction());
            AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(context);
            dialogBuilder.setTitle("警告:");
            dialogBuilder.setMessage("您的账号在别处登录,请重新登陆!");
            dialogBuilder.setCancelable(false);
            dialogBuilder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    ActivityCollector.getInstance().finishAll();
                    Intent intent = new Intent(context, LoginActivity.class);
                    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(intent);
                }
            });
            AlertDialog alertDialog = dialogBuilder.create();
            alertDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY);
            alertDialog.show();
        }
    }
}

我们可以看到,它里面定义了一个alert dialog,这个dialog在弹出时没有context因此我们把它叫作无activity(窗体)依托dialog,因此这种dialog是必须要申请权限的,这是Android的规定。然后这个alert dialog有一个【确定】按钮,点一下这个【确定】按钮,就会以startActivity的方式再次打开activity_main界面,此处我们需要注意的是,这个startActivity里的intent的类型必须为Intent.FLAG_ACTIVITY_NEW_TASK),否则你死活从这个登录界面跳不回activity_main的界面了。

接着看来MainActivity以及里面发生消息的部分(含代码动态申请Android权限)。

MainActivity.java

package org.mk.android.demo.broadcast;
 
import androidx.appcompat.app.AppCompatActivity;
import androidx.localbroadcastmanager.content.LocalBroadcastManager;
 
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.provider.Settings;
import android.util.Log;
import android.view.View;
import android.widget.Button;
 
public class MainActivity extends BaseActivity {
    private BroadCastReceiver localReceiver;
    private LocalBroadcastManager localBroadcastManager;
    private IntentFilter intentFilter;
    private static final String BROADCAST_ACTON = "org.mk.android.demo.broadcast";
    private final String TAG = "BroadCastWithActivity";
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button buttonLoginInOtherPlace = (Button) findViewById(R.id.buttonLoginInOtherPlace);
        localBroadcastManager = LocalBroadcastManager.getInstance(this);
 
        //初始化广播接收者,设置过滤器
        localReceiver = new BroadCastReceiver();
        intentFilter = new IntentFilter();
        intentFilter.addAction(BROADCAST_ACTON);
        localBroadcastManager.registerReceiver(localReceiver, intentFilter);
        buttonLoginInOtherPlace.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (!Settings.canDrawOverlays(MainActivity.this)) {
                    Intent mintent = new Intent();
                    mintent.setAction(Settings.ACTION_MANAGE_OVERLAY_PERMISSION);
                    startActivity(mintent);
                }
 
                Log.i(TAG, ">>>>>>MainActivity->onClick");
                Intent intent = new Intent(BROADCAST_ACTON);
                localBroadcastManager.sendBroadcast(intent);
            }
        });
    }
 
    @Override
    protected void onDestroy() {
        super.onDestroy();
        localBroadcastManager.unregisterReceiver(localReceiver);
    }
}

这边核心注意点:

代码动代申请权限

if (!Settings.canDrawOverlays(MainActivity.this)) {
    Intent mintent = new Intent();
    mintent.setAction(Settings.ACTION_MANAGE_OVERLAY_PERMISSION);
    startActivity(mintent);
}

代码运行到这,Android会打开一个该APP相应的系统权限对话框

然后把这边的Allow手动启用。

接着我们重新运行这个APP,效果如下。

运行效果

点击【确定】登出activity_main切换到activity_login

在这个界面点击【点一下代表登录了】按钮,再次回到activity_main

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