Android 强制下线功能 第一行代码

强制下线功能：先关闭掉所有的活动，然后回到登陆界面

相应工程：http://download.csdn.net/detail/u012005313/9004889

先创建一个ActivityCollector类用于管理所有的活动

package com.example.zj.broadcastbestpractice;

import android.app.Activity;

import java.util.ArrayList;
import java.util.List;

/**
* Created by zj on 15-8-14.
*/
public class ActivityCollector {

public 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();
}
}
}
}

创建BaseActivity类作为所有活动的父类

package com.example.zj.broadcastbestpractice;

import android.app.Activity;
import android.os.Bundle;

/**
* Created by zj on 15-8-14.
*/
public class BaseActivity extends Activity {

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

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

创建一个登陆界面的布局

<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:stretchColumns="1">

<TableRow>
<TextView
android:layout_height="wrap_content"
android:text="Account:"
/>

<EditText
android:id="@+id/account"
android:layout_height="wrap_content"
android:hint="Input your account"
/>
</TableRow>

<TableRow>
<TextView
android:layout_height="wrap_content"
android:text="Password:"
/>

<EditText
android:id="@+id/password"
android:layout_height="wrap_content"
android:inputType="textPassword"
/>
</TableRow>

<TableRow>
<Button
android:id="@+id/login"
android:layout_height="wrap_content"
android:layout_span="2"
android:text="Login"
/>
</TableRow>

</TableLayout>

新建LoginActivity继承自BaseActivity

package com.example.zj.broadcastbestpractice;

import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

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();

if (account.equals("admin") && password.equals("123456")) {
Intent intent = new Intent(LoginActivity.this, MainActivity.class);
Log.i("this", "------------------------intent to MainActivity");
startActivity(intent);
finish();
} else {
Toast.makeText(LoginActivity.this, "account or password error", Toast.LENGTH_SHORT).show();
}
}
});
}
}

从上面代码可知，我们模拟了一个非常简单的登陆功能

用户名：admin

密码：123456

MainActivity可理解为登录成功后的程序主界面，在主界面设置一个按钮，增加强制下线的功能

修改activity_main.xml代码

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<Button
android:id="@+id/force_offline"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Send force offline broadcast"
/>

</LinearLayout>

修改MainActivity代码

package com.example.zj.broadcastbestpractice;

import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;

public class MainActivity extends Activity {

@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.zj.broadcastbestpractice.FORCE_OFFLINE");
sendBroadcast(intent);
}
});
}
}

重点：我们在按钮的点击事件里发送一条广播，广播值为

com.zj.broadcastbestpractice.FORCE_OFFLINE

这条广播就是用于通知程序强制用户下线的，也就是说强制用户下线的逻辑并不是写在MainActivity里面，而是应该写在接受这条广播的广播接收器里面，这样强制下线的功能就不会依附于任何的界面，不管是在程序的任何地方，只需要发出这样一条广播，就可以完成强制下线的操作

创建一个广播接收器，新建ForceOfflineReceiver继承自BroadcastReceiver

package com.example.zj.broadcastbestpractice;

import android.app.AlertDialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.view.WindowManager;

/**
* Created by root on 15-8-14.
*/
public class ForceOfflineReceiver extends BroadcastReceiver {

@Override
public void onReceive(final Context context, Intent intent) {
AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(context);
dialogBuilder.setTitle("Warning");
dialogBuilder.setMessage("You are forced to be offline.  Please try to login again.");
dialogBuilder.setCancelable(false);
dialogBuilder.setPositiveButton("OK", 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();
}
}

要点：

首先使用AlertDialog.Builder来构建一个对话框（调用setCancelable()方法将对话框设为不可取消，否则用户按一下Back键就可以关闭对话框继续使用程序）

然后使用setPositiveButton()方法给对话框注册确定按钮，当用户点击了确定按钮时，就调用ActivityCollector的finishAll()方法来销毁所有的活动，并重新启动LoginActivity

note：由于我们是在广播接收器里启动活动，因此一定要给Intent加入FLAG_ACTIVITY_NEW_TASK这个标志，最后，还需要把对话框的类型设为TYPE_SYSTEM_ALERT，不然无法在广播接收器中弹出

配置AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.zj.broadcastbestpractice" >

<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
</activity>
<activity
android:name=".LoginActivity"
android:label="@string/title_activity_login" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

<receiver android:name=".ForceOfflineReceiver" >
<intent-filter>
<action android:name="com.zj.broadcastbestpractice.FORCE_OFFLINE" />
</intent-filter>
</receiver>
</application>

</manifest>

完成，启动项目