本地廣播

Android中給我們提供了本地廣播的機制，使用該機制發出的廣播只會在APP內部傳播，而且 廣播接收者也只能收到本應用發出的廣播！

1.注意事項

1. 本地廣播無法通過靜態註冊來接收，相比系統全局廣播更加高效！
2. 在廣播中啓動Activity的話需要爲intent加入FLAG_ACTIVITY_NEW _TAG的標記，不然會報錯。
3. 廣播中彈出AlertDialog的話，需要設置對話框的類型爲TYPE_SYSTEM_ALERT，不然無法彈出。

2.核心用法
使用LocalBroadcastManager 來管理廣播：

1. 調用LocalBroadcastManager.getInstance()獲得實例
2. 調用~.registerReceiver註冊廣播
3. 調用~.sendBroadcast()發送廣播
4. 調用~.unregisterReceiver取消註冊
   PS:~代表LocalBroadcastManager 實例

3.代碼示例
直接貼小豬代碼
Step 1：準備一個關閉所有Activity的ActivityCollector

ActivityCollector.java

public class ActivityCollector {
    private static List<Activity> activities = new ArrayList<Activity>();
    public static void addActivity(Activity activity) {
        activities.add(activity);
    }
    public static void removeActivity(Activity activity) {
        activities.remove(activity);
    }
    public static void finishAll() {
        for (Activity activity : activities) {
            if (!activity.isFinishing()) {
                activity.finish();
            }
        }
    }
}

Step 2：先寫要給簡單的BaseActivity，用來繼承，接着寫下登陸界面！

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

    @Override
    protected void onDestroy() {
        super.onDestroy();
        ActivityCollector.removeActivity(this);
    }
}

LoginActivity.java:

public class LoginActivity extends BaseActivity implements View.OnClickListener{


    private SharedPreferences pref;
    private SharedPreferences.Editor editor;

    private EditText edit_user;
    private EditText edit_pawd;
    private Button btn_login;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        pref = PreferenceManager.getDefaultSharedPreferences(this);

        bindViews();
    }

    private void bindViews() {
        edit_user = (EditText) findViewById(R.id.edit_user);
        edit_pawd = (EditText) findViewById(R.id.edit_pawd);
        btn_login = (Button) findViewById(R.id.btn_login);
        btn_login.setOnClickListener(this);
    }

    @Override
    protected void onStart() {
        super.onStart();
        if(!pref.getString("user","").equals("")){
            edit_user.setText(pref.getString("user",""));
            edit_pawd.setText(pref.getString("pawd",""));
        }
    }

    @Override
    public void onClick(View v) {
        String user = edit_user.getText().toString();
        String pawd = edit_pawd.getText().toString();
        if(user.equals("123")&&pawd.equals("123")){
            editor = pref.edit();
            editor.putString("user", user);
            editor.putString("pawd", pawd);
            editor.commit();
            Intent intent = new Intent(LoginActivity.this, MainActivity.class);
            startActivity(intent);
            Toast.makeText(LoginActivity.this,"喲，竟然蒙對了~",Toast.LENGTH_SHORT).show();
            finish();
        }else{
            Toast.makeText(LoginActivity.this,"這麼簡單都輸出，腦子呢？",Toast.LENGTH_SHORT).show();
        }

    }
}

Step 3：自定義一個BroadcastReceiver，在onReceive裏完成彈出對話框操作，以及啓動登陸頁面：

MyBcReceiver.java

public class MyBcReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(final Context context, Intent intent) {
        AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(context);
        dialogBuilder.setTitle("警告：");
        dialogBuilder.setMessage("您的賬號在別處登錄，請重新登陸~");
        dialogBuilder.setCancelable(false);
        dialogBuilder.setPositiveButton("確定",
                new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        ActivityCollector.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_SYSTEM_ALERT);
        alertDialog.show();
    }
}

AndroidManifest.xml

< uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

Step 4：在MainActivity中，實例化localBroadcastManager，拿他完成相關操作，另外銷燬時 注意unregisterReceiver！

MainActivity.java

public class MainActivity extends BaseActivity {

    private MyBcReceiver localReceiver;
    private LocalBroadcastManager localBroadcastManager;
    private IntentFilter intentFilter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        localBroadcastManager = LocalBroadcastManager.getInstance(this);

        //初始化廣播接收者，設置過濾器
        localReceiver = new MyBcReceiver();
        intentFilter = new IntentFilter();
        intentFilter.addAction("com.jay.mybcreceiver.LOGIN_OTHER");
        localBroadcastManager.registerReceiver(localReceiver, intentFilter);

        Button btn_send = (Button) findViewById(R.id.btn_send);
        btn_send.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent("com.jay.mybcreceiver.LOGIN_OTHER");
                localBroadcastManager.sendBroadcast(intent);
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        localBroadcastManager.unregisterReceiver(localReceiver);
    }
}