BroadcastBestPractise

学习目的：实现登陆成功后强制下线功能(关闭所有活动，返回登陆界面)

1.新建ActivityCollector类

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 (!activity.isFinishing()) {
                activity.finish();
            }
        }
    }

}

2.创建BaseActivity类作为所有活动的父类

public class BaseActivity extends AppCompatActivity {

    private ForceOfflineReceiver receiver;

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

3.新建LoginActivity类及其布局(登陆的处理)

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();
                // 如果账号是admin且密码是123456，就认为登录成功
                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();
                }
            }
        });
    }

}

4.修改MainACTIVITY类及其布局

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);//发送com.example.broadcastbestpractice.FORCE_OFFLINE广播 表示强制下线
                //需要创建广播接收器
            }
        });
    }

}

在BaseActivity类注册广播接收器

public class BaseActivity extends AppCompatActivity {

    private ForceOfflineReceiver receiver;

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

    @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 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);//创建一个对话框
            builder.setTitle("Warning");
            builder.setMessage("You are forced to be offline. Please try to login again.");
            builder.setCancelable(false);
            //注册确定按钮
            builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {//给ok按钮设置点击事件
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    ActivityCollector.finishAll(); // 销毁所有活动
                    Intent intent = new Intent(context, LoginActivity.class);
                    context.startActivity(intent); // 重新启动LoginActivity
                }
            });
            builder.show();
        }

    }

}

将LoginActivity作为主界面

<activity android:name=".LoginActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
```    

完工!




chaper6 实现记住密码功能
```java
public class LoginActivity extends BaseActivity {

    private SharedPreferences pref;

    private SharedPreferences.Editor editor;

    private EditText accountEdit;

    private EditText passwordEdit;

    private Button login;

    private CheckBox rememberPass;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        pref = PreferenceManager.getDefaultSharedPreferences(this);
        accountEdit = (EditText) findViewById(R.id.account);
        passwordEdit = (EditText) findViewById(R.id.password);
        rememberPass = (CheckBox) findViewById(R.id.remember_pass);
        login = (Button) findViewById(R.id.login);
        boolean isRemember = pref.getBoolean("remember_password", false);
        if (isRemember) {
            // 将账号和密码都设置到文本框中
            String account = pref.getString("account", "");
            String password = pref.getString("password", "");
            accountEdit.setText(account);
            passwordEdit.setText(password);
            rememberPass.setChecked(true);
        }
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String account = accountEdit.getText().toString();
                String password = passwordEdit.getText().toString();
                // 如果账号是admin且密码是123456，就认为登录成功
                if (account.equals("admin") && password.equals("123456")) {
                    editor = pref.edit();
                    if (rememberPass.isChecked()) { // 检查复选框是否被选中
                        editor.putBoolean("remember_password", true);
                        editor.putString("account", account);
                        editor.putString("password", password);
                    } else {
                        editor.clear();
                    }
                    editor.apply();
                    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();
                }
            }
        });
    }

}