Android的广播机制实践--强制下线功能的实现

ゞ浴缸里的玫瑰 2022-05-23 09:24 194阅读 0赞

强制下线功能实现是关闭所有活动，回到登录界面。  
先展示效果图：  
![这里写图片描述][70]  
![这里写图片描述][70 1]  
点击off即可回到登录界面。  
下面给出逻辑代码。  
1.登录界面布局

<?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" android:background="@drawable/a">
    
        <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginTop="40dp">
            <TextView android:layout_width="80dp" android:layout_height="40dp" android:text="账号" android:textColor="#000000" android:textSize="35sp"/>
    
            <EditText android:layout_width="0dp" android:layout_height="40dp" android:layout_weight="1" android:hint="请输入账号" android:id="@+id/et_user"/>
        </LinearLayout>
    
        <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginTop="40dp">
            <TextView android:layout_width="80dp" android:layout_height="40dp" android:text="密码" android:textColor="#000000" android:textSize="35sp"/>
    
            <EditText android:layout_width="0dp" android:layout_height="40dp" android:layout_weight="1" android:hint="请输入密码" android:id="@+id/et_password"/>
        </LinearLayout>
    
        <Button android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginTop="40dp" android:id="@+id/btn_login" android:text="登录"/>
    
    </LinearLayout>

2.登录的逻辑功能，这里我们规定用户名为admin，密码为12345，否则登录失败

public class loginActivity extends AppCompatActivity{ 
        private EditText tv_user,tv_pass;
        private Button btn_login;
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.login_layout);
    
            tv_user=(EditText)findViewById(R.id.et_user);
            tv_pass=(EditText)findViewById(R.id.et_password);
            btn_login=(Button)findViewById(R.id.btn_login);
    
            btn_login.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    String user=tv_user.getText().toString();
                    String pass=tv_pass.getText().toString();
                    if(user.equals("admin")&&pass.equals("12345")){
                        startActivity(new Intent(loginActivity.this,ActivityText.class));
                        //ActivityText是一个只有一个 button的布局，点击button即可发送广播
                    }else{
                        Toast.makeText(loginActivity.this, "账号或密码不正确", Toast.LENGTH_SHORT).show();
                    }
                }
            });
        }
    }

3.广播的发送

public class ActivityText extends BroadCast { 
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.off_layout);
    
            Button button=(Button)findViewById(R.id.btn_off);
            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent intent=new Intent("com.exaple.loginOff");
                    sendBroadcast(intent);
                }
            });
        }
    }

4.广播接收及强制下线功能实现  
强制下线需要关闭所有活动。先写一个实体类用来用来实现关闭活动的功能

public class ActivityCollector {
        public static List<Activity> sActivities=new ArrayList<>();
        public static void addACtivity(Activity activity){
            sActivities.add(activity);
        }
    
        public static void removeActivity(Activity activity){
            sActivities.remove(activity);
        }
    
        public static void finishiAll(){
            for(Activity activity:sActivities){
                if(!activity.isFinishing()){
                    activity.finish();
                }
            }
            sActivities.clear();
        }
    }

接下来就是广播接收和活动关闭。

public class BroadCast extends AppCompatActivity{ 
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            ActivityCollector.addACtivity(this);
        }
    
    //注册广播
        @Override
        protected void onResume() {
            super.onResume();
            IntentFilter intentFilter=new IntentFilter();
            intentFilter.addAction("com.exaple.loginOff");
            registerReceiver(mBroadcastReceiver,intentFilter);
        }
    
        @Override
        protected void onDestroy() {
            super.onDestroy();
            ActivityCollector.removeActivity(this);
        }
    //取消广播
        @Override
        protected void onPause() {
            super.onPause();
            if(mBroadcastReceiver!=null){
                unregisterReceiver(mBroadcastReceiver);
                mBroadcastReceiver=null;
            }
        }
    
    //广播一接收就弹出一个dialog，点击ok按钮跳转到login界面，并且关闭所有活动。
        private BroadcastReceiver mBroadcastReceiver=new BroadcastReceiver() {
            @Override
            public void onReceive(final Context context, Intent intent) {
                AlertDialog.Builder builder=new AlertDialog.Builder(context);
                builder.setMessage("login off");
                builder.setTitle("warning");
                builder.setPositiveButton("ok", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        ActivityCollector.finishiAll();
                        startActivity(new Intent(context,loginActivity.class));
                    }
                });
                builder.show();
            }
        };
    }

广播的生命周期很短，一般不超过十秒，所以一般不在广播接收时实现太多的功能。

[70]: /images/20220523/5a938bbb2b2f4a89941fb66dfd661450.png
[70 1]: /images/20220523/f79d97fe7e83445fb836f09ea575ef04.png