在Android开发时，有时因为需求，需要跳转到系统的一些页面，比如从UI中跳转到系统设置项、WIFI设置等，那要如何返回到原来的Activity中呢？
我们可以通过WindowManager来实现。原理可以简单的理解为在跳转到系统的Activity中后，在该Activity的上方添加一个按钮，然后对这个按钮添加事件。
先看看效果图
实现代码如下
CallSystemActivity.java
package com.example.callsystemactivity;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Init(); } private void Init() { Button callSystemSet_button=(Button)findViewById(R.id.CallSystemSet_button); callSystemSet_button.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub WindowManagerSp windowManagerSp=new WindowManagerSp(MainActivity.this); windowManagerSp.AddBackButton(); IntentSp.StartActivity(MainActivity.this, android.provider.Settings.ACTION_WIFI_IP_SETTINGS,false); } }); }} 注：
1、需要在activity_main.xml中添加一个按钮callSystemSet_button
2、WindowManager需要相应的权限，所以需要在AndroidManifest.xml中添加权限，如下
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
<uses-permission android:name="android.permission.SYSTEM_OVERLAY_WINDOW" />WindowManagerSp.java
package com.example.callsystemactivity;import android.app.Activity;import android.content.Context;import android.view.Gravity;import android.view.View;import android.view.View.OnClickListener;import android.view.WindowManager;import android.widget.ImageView;public class WindowManagerSp { WindowManager _winManager = null; Activity _activity = null; Context _context = null; public WindowManagerSp(Activity activity) { if (activity == null) { return; } _activity = activity; _context = _activity.getBaseContext(); _winManager = (WindowManager) _activity.getApplicationContext() .getSystemService(_activity.WINDOW_SERVICE); } public void AddBackButton() { if (_winManager == null) { return; } WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(); layoutParams.gravity = Gravity.TOP | Gravity.LEFT; layoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE; layoutParams.type = WindowManager.LayoutParams.TYPE_SYSTEM_ALERT | WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY; // 以下width/height/x/y不一定是最合适的，需根据实现的页面加以调整 layoutParams.width = 32; layoutParams.height = 32; layoutParams.x = 280; layoutParams.y = 0; final ImageView backButton = new ImageView(_context); backButton.setBackgroundResource(R.drawable.back);// 请自行添加相应的背景图片 backButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { IntentSp.RestartActivity(_activity, false);// 在另一个类中 if (_winManager != null) { _winManager.removeView(backButton); } _winManager = null; } }); _activity.finish();// 关闭activity，在返回时再次开启 _winManager.addView(backButton, layoutParams); }} IntentSp.java
package com.kitsp.contentsp;import android.app.Activity;import android.content.ComponentName;import android.content.Context;import android.content.Intent;import android.net.Uri;public class IntentSp { /** * * @param activity * @param isSaveActivityToHistory * true:save activity to history.System may back to the activity * when other activity finish. false:no save. */ public static void RestartActivity(Activity activity, boolean isSaveActivityToHistory) { if (activity == null) { return; } Intent intent = new Intent(); String packageName = activity.getPackageName(); String className = activity.getLocalClassName(); String componentClassName = packageName + "." + className; if (className != null && className.split(".").length > 0) { componentClassName = className; } ComponentName componentName = new ComponentName(packageName, componentClassName); intent.setComponent(componentName); if (!isSaveActivityToHistory) { intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);//添加该标志后，让activity不保存 } activity.startActivity(intent); activity.finish(); return; }/** * * @param context * @param action * @param isSaveActivityToHistory * true:save activity to history.System may back to the activity * when other activity finish. false:no save. */ public static void StartActivity(Context context, String action, boolean isSaveActivityToHistory) { if (context == null || action == null) { return; } Intent intent = new Intent(action); if (!isSaveActivityToHistory) { intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY); } context.startActivity(intent); }}注： intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY)是为了不让系统的activity在开启后一直存在，如果不这样处理，在点硬返回键时，才不会返回到系统的activity中。因为由A应用开启B应用的Activity，正常是无法从A中关闭B应用的Activity的，对于我们启动系统的Activity也是一样的道理。所以为了避免该问题，我们增加了flag，这样启动后的activity就不会保存到activity的堆栈中，自然在点返回时，也就不会返回到该activity中了。