Android廣播時間——實現強制下線功能

時間 2020-05-14

原文原文鏈接

思路:強制下線功能須要先關閉掉全部的活動，而後回到登陸界面。

步驟

新建BroadcastBestPractice項目java

1.關閉全部活動

建立ActivityCollector類管理全部的活動，代碼以下:android

public class ActivityCollector {

    public static List<Activity> activities=new ArrayList<>();

    public static void addActivity(Activity activity){
        activities.add(activity);
    }
    public static void removeActivity(Activity activity){
        activities.remove(activity);
    }
    //關閉全部活動
    public static void finishAll(){
        for (Activity activity:activities) {
            if(!activity.isFinishing())
                activity.finish();
        }
        activities.clear();
    }
}

2.建立BaseActivity類做爲全部活動的父類，由於須要用ActivityCollector管理全部活動代碼以下:

public class BaseActivity extends AppCompatActivity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityCollector.addActivity(this);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        ActivityCollector.removeActivity(this);
    }
}

3.建立登陸界面活動，新建LoginActivity，編輯其佈局文件:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:orientation="horizontal">
        <TextView
            android:layout_width="90dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:textSize="18sp"
            android:text="Account:"/>
        <EditText
            android:id="@+id/account"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_gravity="center_vertical"/>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:orientation="horizontal">
        <TextView
            android:layout_width="90dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:textSize="18sp"
            android:text="Password:"/>
        <EditText
            android:id="@+id/password"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_gravity="center_vertical"
            android:inputType="textPassword"/>
    </LinearLayout>
    <Button
        android:id="@+id/login"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:text="Login"/>
</LinearLayout>

最外層是縱向的LinearLayout，裏面包含三行子元素。第一行是橫向的LinearLayout，用於輸入帳號信息。第二行是橫向的LinearLayout，用於輸入密碼。第三行是一個按鈕，用來登陸。app

接下來修改LoginActivity中的代碼:ide

public class LoginActivity extends BaseActivity {
    private EditText accountEdit;
    private EditText passwordEdit;
    private Button login;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        accountEdit=(EditText)findViewById(R.id.account);
        passwordEdit=(EditText)findViewById(R.id.password);
        login=(Button)findViewById(R.id.login);
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String account=accountEdit.getText().toString();
                String password=passwordEdit.getText().toString();
                //若是帳號是admin且密碼是123456，就認爲登陸成功
                if(account.equals("admin")&&password.equals("123456")){
                    Intent intent=new Intent(LoginActivity.this,MainActivity.class);//跳轉到MainActivity
                    startActivity(intent);
                    finish();
                }else{
                    Toast.makeText(LoginActivity.this,"account or password is invald",Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}

4.修改activity_main.xml中的代碼和MainActivity(全部的活動都要繼承BaseActivity)中的代碼，加入強制下線功能

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/force_offline"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Send force offline broadcast"/>
</LinearLayout>

public class MainActivity extends BaseActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button forceoffline=(Button)findViewById(R.id.force_offline);
        forceoffline.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent =new Intent("com.example.broadcastbestpractice.FORCE_OFFLINE");
                sendBroadcast(intent);
            }
        });
    }
}

代碼十分簡單但這裏有個重點，咱們點擊按鈕發送廣播com.example.broadcastbestpractice.FORCE_OFFLINE。經過這個廣播，咱們實現強制下線，這樣強制下線功能不會依附任何界面，無論在程序任何地方，只要發出這樣一條廣播，就能夠完成強制下線操做。佈局

5.建立廣播接收器

因爲廣播接收器須要彈出一個對話框來阻塞用戶的正常操做，但若是建立的是一個靜態註冊的廣播接收器，是沒法在onReceive()方法中彈出對話框這樣的UI控件的（爲何?）。而咱們也不能在每一個活動中都去註冊這樣一個廣播接收器。可是這個時候，咱們能夠在BaseActivity中建立一個廣播接收器就能夠實現全部的活動中都有.（由於全部的活動都繼承自BaseActivity)ui

public class BaseActivity extends AppCompatActivity {
    private ForceOffLineReceiver receiver;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityCollector.addActivity(this);
    }
    //註冊寫在onResume()中
    @Override
    protected void onResume() {
        super.onResume();
        IntentFilter intentFilter=new IntentFilter();
        intentFilter.addAction("com.example.a51104.broadcastbestpractice.FORCE_OFFLINE");
        receiver=new ForceOffLineReceiver();
        registerReceiver(receiver,intentFilter);
    }
    //取消註冊寫在onPause()中，由於只有棧頂活動才須要接收那個廣播
    @Override
    protected void onPause() {
        super.onPause();
        if(receiver!=null){
            unregisterReceiver(receiver);
            receiver=null;
        }
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        ActivityCollector.removeActivity(this);
    }
    class ForceOffLineReceiver extends BroadcastReceiver{
        @Override
        public void onReceive(final Context context, Intent intent) {
            AlertDialog.Builder builder=new AlertDialog.Builder(context);
            builder.setTitle("Warning");
            builder.setMessage("You are forced to be offLine.Please try to login again");
            builder.setCancelable(false);//設置爲不可取消
            builder.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    ActivityCollector.finishAll();//取消全部活動
                    Intent i=new Intent(context,LoginActivity.class);
                    context.startActivity(i);//從新啓動LoginActivity
                }
            });
            builder.show();
        }
    }
}

6.修改AndroidManifest.xml，將LoginActivity設置爲主活動

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.broadcastbestpractice">
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
        </activity>
        <activity android:name=".LoginActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>