之前有个需求,App从前台切换到后台,不需要做什么操作;从后台切换到前台,需要先验证屏锁密码。于是乎,搜索了一下,“利用Application监听App处于前台和后台”,找到了一个国外的big god的解决方案。不要问我是怎么找到的,做开发必备的技能,擅长检索,也是一种能力。致谢steveliles
…
废话不说了,直接上代码。
<pre>
public class ForegroundCallbacks implements Application.ActivityLifecycleCallbacks {
public static final long CHECK_DELAY = 500;
public static final String TAG = ForegroundCallbacks.class.getName();
public interface Listener {
public void onBecameForeground();
public void onBecameBackground();
}
private static ForegroundCallbacks instance;
private boolean foreground = false, paused = true;
private Handler handler = new Handler();
private List<Listener> listeners = new CopyOnWriteArrayList<Listener>();
private Runnable check;
public static ForegroundCallbacks init(Application application){
if (instance == null) {
instance = new ForegroundCallbacks();
application.registerActivityLifecycleCallbacks(instance);
}
return instance;
}
public static ForegroundCallbacks get(Application application){
if (instance == null) {
init(application);
}
return instance;
}
public static ForegroundCallbacks get(Context ctx){
if (instance == null) {
Context appCtx = ctx.getApplicationContext();
if (appCtx instanceof Application) {
init((Application)appCtx);
}
throw new IllegalStateException(
"Foreground is not initialised and " +
"cannot obtain the Application object");
}
return instance;
}
public static ForegroundCallbacks get(){
if (instance == null) {
throw new IllegalStateException(
"Foreground is not initialised - invoke " +
"at least once with parameterised init/get");
}
return instance;
}
public boolean isForeground(){
return foreground;
}
public boolean isBackground(){
return !foreground;
}
public void addListener(Listener listener){
listeners.add(listener);
}
public void removeListener(Listener listener){
listeners.remove(listener);
}
@Override
public void onActivityResumed(Activity activity) {
paused = false;
boolean wasBackground = !foreground;
foreground = true;
if (check != null)
handler.removeCallbacks(check);
if (wasBackground){
LogUtil.e("went foreground");
for (Listener l : listeners) {
try {
l.onBecameForeground();
} catch (Exception exc) {
LogUtil.e("Listener threw exception!", exc);
}
}
} else {
LogUtil.e("still foreground");
}
}
@Override
public void onActivityPaused(Activity activity) {
paused = true;
if (check != null)
handler.removeCallbacks(check);
handler.postDelayed(check = new Runnable(){
@Override
public void run() {
if (foreground && paused) {
foreground = false;
LogUtil.e("went background");
for (Listener l : listeners) {
try {
l.onBecameBackground();
} catch (Exception exc) {
LogUtil.e("Listener threw exception!", exc);
}
}
} else {
LogUtil.e("still foreground");
}
}
}, CHECK_DELAY);
}
@Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {}
@Override
public void onActivityStarted(Activity activity) {}
@Override
public void onActivityStopped(Activity activity) {}
@Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {}
@Override
public void onActivityDestroyed(Activity activity) {}
}
</pre>