MainActivity如下:
package cc.testbackgroundtofront;
import java.util.List;
import android.app.Activity;
import android.app.ActivityManager;
import android.app.ActivityManager.RunningTaskInfo;
import android.content.ComponentName;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.widget.Toast;
/**
* Demo描述:
* 判断应用从后台回到前台
* 即按下Home键后重新进入到应用
*/
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
@Override
protected void onResume() {
super.onResume();
}
@Override
protected void onRestart() {
super.onRestart();
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
boolean isCurrentRunningForeground = prefs.getBoolean("isCurrentRunningForeground", false);
if (!isCurrentRunningForeground) {
Toast.makeText(MainActivity.this, "从后台回来", Toast.LENGTH_SHORT).show();
}
}
@Override
protected void onStop() {
super.onStop();
try {
Thread.sleep(1000);
new Thread(){
public void run() {
boolean isCurrentRunningForeground=isRunningForeground();
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
Editor editor=prefs.edit();
editor.putBoolean("isCurrentRunningForeground", isCurrentRunningForeground);
editor.commit();
};
}.start();
} catch (Exception e) {
}
}
public boolean isRunningForeground(){
String packageName=getPackageName(this);
String topActivityClassName=getTopActivityName(this);
System.out.println("packageName="+packageName+",topActivityClassName="+topActivityClassName);
if (packageName!=null&&topActivityClassName!=null&&topActivityClassName.startsWith(packageName)) {
System.out.println("---> isRunningForeGround");
return true;
} else {
System.out.println("---> isRunningBackGround");
return false;
}
}
public String getTopActivityName(Context context){
String topActivityClassName=null;
ActivityManager activityManager =
(ActivityManager)(context.getSystemService(android.content.Context.ACTIVITY_SERVICE )) ;
//android.app.ActivityManager.getRunningTasks(int maxNum)
//int maxNum--->The maximum number of entries to return in the list
//即最多取得的运行中的任务信息(RunningTaskInfo)数量
List<RunningTaskInfo> runningTaskInfos = activityManager.getRunningTasks(1) ;
if(runningTaskInfos != null){
ComponentName f=runningTaskInfos.get(0).topActivity;
topActivityClassName=f.getClassName();
}
//按下Home键盘后 topActivityClassName=com.android.launcher2.Launcher
return topActivityClassName;
}
public String getPackageName(Context context){
String packageName = context.getPackageName();
return packageName;
}
}
main.xml如下:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="判断应用是否是由后台回到前台"
android:layout_centerInParent="true"
/>
</RelativeLayout>
