广播的最佳实例

创建AcitivityCollector类

管理所有活动

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);
    }

    public static void finishAll(){
        for(Activity activity:activities){
            if(!activities.isEmpty()){
                activity.finish();
            }
        }
    }
}

创建BaseActivity作为所有活动父类

public class BaseActivity extends AppCompatActivity {

    private ForceOffLineReceiver receiver;

    @Override
    protected void onResume() {
        super.onResume();
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction("com.example.broadcastbestpractice.FORCE_OFFLINE");
        receiver = new ForceOffLineReceiver();
        registerReceiver(receiver,intentFilter);
    }

    @Override
    protected void onPause() {
        super.onPause();
        if(receiver!=null){
            unregisterReceiver(receiver);
            receiver = null;
        }
    }

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityCollector.addActivity(this);
    }

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

    class ForceOffLineReceiver extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            AlertDialog.Builder builder = new AlertDialog.Builder(context);
            builder.setTitle("Warning");
            builder.setMessage("You are forced to be offline");
            builder.setCancelable(false);
            builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    ActivityCollector.finishAll();
                    Intent intent = new Intent(context,LoginActivity.class);
                    context.startActivity(intent);
                }
            });
            builder.show();
        }
    }
}

ForceOfflineReceiver

1. 使用AlertDialog.Builder来构建一个对话框
2. 调用setCancelable（）方法将对话框设置为不可取消
3. 调用setPositiveButton（）方法来给对话框注册确定按钮

修改LoginActivity类

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 = findViewById(R.id.account);
        passwordEdit = findViewById(R.id.password);
        login = findViewById(R.id.login);
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String account = accountEdit.getText().toString();
                String password = passwordEdit.getText().toString();
                //密码是123456.用户名为admin
                if(account.equals("admin")&&password.equals("123456")){
                    Intent intent = new Intent(LoginActivity.this,MainActivity.class);
                    startActivity(intent);
                    finish();
                }else{
                    Toast.makeText(LoginActivity.this,"account or password is invalid",Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}

修改MainActivity中的代码

public class MainActivity extends BaseActivity {

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