Android判断当前App应用处于前台(可见)或后台(不可见)

也即判断当前App应用是否被用户按home键切换至后台（不可见）/前台（可见）。

package zhangphil.test; import android.app.ActivityManager;; import android.content.Context; import android.os.Bundle; import android.support.annotation.Nullable; import android.support.v7.app.AppCompatActivity; import java.util.List; import java.util.concurrent.TimeUnit; public class JavaActivity extends AppCompatActivity { private ActivityManager activityManager; private String packageName; private boolean stop = false; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); //setContentView(R.layout.drawable_activity); activityManager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE); packageName = this.getPackageName(); new Thread(new AppStatus()).start(); } private class AppStatus implements Runnable { @Override public void run() { stop = false; while (!stop) { try { if (appOnForeground()) { System.out.println("当前App处于前台"); } else { System.out.println("当前App处于后台"); } } catch (Exception e) { e.printStackTrace(); } try { TimeUnit.SECONDS.sleep(1); } catch (Exception e) { e.printStackTrace(); } } } } private boolean appOnForeground() { List<ActivityManager.RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses(); if (appProcesses == null) return false; for (ActivityManager.RunningAppProcessInfo appProcess : appProcesses) { if (appProcess.processName.equals(packageName) && appProcess.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) { return true; } } return false; } }

以上这个方案是全局性的判断当前App是否处于前台可见，抑或后台不可见。

需要明白的一点儿是，在大型Android项目中，存在很多Activity时候，仅靠让全部Activity继承自一个类似Base的Activity，然后在Base的Activity生命周期中做相应逻辑处理，进而判断当前App是否处于前台后台的方法是不可取行不通的。