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我必须使用本机库(这不是我的决定)。该库已经有一个 JNI 包装器,并且示例 Android NDK 代码有效。但库初始化例程返回本地句柄,开发人员需要正确关闭它们

现在,有一个有趣的问题:从哪里调用 close_handle 例程?

至少在理论上,每次不正确的终止都可能导致临时文件留在磁盘上的某处或某种其他类型的资源泄漏。

库初始化需要 0.5 到 1 秒,并且会消耗大量内存。

anActivity是一个控制器(MVC 意义上的),Android 可以因为自己的原因杀死它,包括转动设备,并且唯一保证被调用的函数是onPause(). 所以onPause/onResume对于长时间的资源消耗操作来说是一个不好的地方。

(我知道android:configChanges="keyboardHidden|orientation",但我更喜欢不需要它的解决方案。)

Application将是一个理想的候选人(我认为库是模型的一部分),但没有“应用程序终止”事件。

Service听起来很有希望,本机库是一项服务,但我只是不明白如何才能获得所需的行为:当应用程序终止时必须关闭句柄。

超时:听起来像是一种权衡,但实际上它保证了内存在需要的那一刻不可用,但几秒钟后就会变得可用。

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2 回答 2

1

现在,看起来我确实需要一个服务,但不完全是IntentService: IntentServicecalls stopSelf(),而我的服务应该挂起。

有趣的Service.onDestroy()是,当用户从“运行服务”中选择“停止”时调用,而不是当用户从“应用程序”中选择“强制停止”时调用。“停止调试”也不会导致Service.onDestroy()调用。

编辑:

我目前的解决方案是使用从自定义子类派生的Service类;IntentService该代码是从“网络”某处的来源借来的。在派生的子类中,我重写onDestroy()并相信这是可用的最佳应用程序终止通知。

package com.xyz.customandroid;

import android.app.Service;
import android.content.Intent;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.IBinder;
import android.os.Looper;
import android.os.Message;

public abstract class HangAroundIntentService extends Service {
    /** An extra with this name and the value of boolean true marks an intent as a cancel intent. See {@link #markedAsCancelIntent(Intent)}. */
    private static final String CANCEL_MARK = "com.xyz~.customandroid.HangAroundIntentService.cancelQueue()";
    private static final int WHAT_MAGIC = 0; // the "what" field for messages
    private volatile Looper mServiceLooper;
    private volatile ServiceHandler mServiceHandler;
    private String mName;
    private boolean mRedelivery;
    private boolean mHangAround = true;

    private final class ServiceHandler extends Handler {
    public ServiceHandler(Looper looper) {
        super(looper);
    }

    @Override
    public void handleMessage(Message msg) {
        onHandleIntent((Intent)msg.obj);
        if (!mHangAround) {
            stopSelf(msg.arg1);
        }
    }
    }

    /**
     * Creates an IntentService.  Invoked by your subclass's constructor.
     *
     * @param name Used to name the worker thread, important only for debugging.
     */
    public HangAroundIntentService(String name) {
    super();
    mName = name;
    }

    /**
     * Remove all pending messages from the handler queue.
     * Processing of the message already fetched from the queue 
     * is not terminated by this function.
     *
     * Although this function is public, it is recommended 
     * to use the cancel intents instead.
     * see {@link #markedAsCancelIntent(Intent)} and {@link #isCancelIntent(Intent)}.
     */
    public void cancelQueue() {
        mServiceHandler.removeMessages(WHAT_MAGIC);
    }

    /**
     * Sets intent redelivery preferences.  Usually called from the constructor
     * with your preferred semantics.
     *
     * <p>If enabled is true,
     * {@link #onStartCommand(Intent, int, int)} will return
     * {@link Service#START_REDELIVER_INTENT}, so if this process dies before
     * {@link #onHandleIntent(Intent)} returns, the process will be restarted
     * and the intent redelivered.  If multiple Intents have been sent, only
     * the most recent one is guaranteed to be redelivered.
     *
     * <p>If enabled is false (the default),
     * {@link #onStartCommand(Intent, int, int)} will return
     * {@link Service#START_NOT_STICKY}, and if the process dies, the Intent
     * dies along with it.
     */
    public void setIntentRedelivery(boolean enabled) {
    mRedelivery = enabled;
    }

    /** 
     * If enabled is true (default), the service does not stop after processing an intent.
     */
    public void setServiceHangAround(boolean enabled) {
    mHangAround = enabled;
    }

    @Override
    public void onCreate() {
    // TODO: It would be nice to have an option to hold a partial wakelock
    // during processing, and to have a static startService(Context, Intent)
    // method that would launch the service & hand off a wakelock.

    super.onCreate();
    HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");
    thread.start();

    mServiceLooper = thread.getLooper();
    mServiceHandler = new ServiceHandler(mServiceLooper);
    }

    /**
     * If intent is a cancel intent, {@link #cancelQueue()} is invoked immediately;
     * no other action is done for a cancel intent, whatever information it might contain.
     * 
     * Intents that are not cancel intents are queued 
     * to be seen from {@link #onHandleIntent(Intent)}.
     */
    @Override
    public void onStart(Intent intent, int startId) {
        if (isCancelIntent(intent)) {
            cancelQueue();
        } else {
        Message msg = mServiceHandler.obtainMessage(WHAT_MAGIC);
        msg.arg1 = startId;
        msg.obj = intent;
        mServiceHandler.sendMessage(msg);
        }
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
    onStart(intent, startId);
    return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;
    }

    @Override
    public void onDestroy() {
    mServiceLooper.quit();
    }

    @Override
    public IBinder onBind(Intent intent) {
    return null;
    }

    /**
     * This method is invoked on the worker thread with a request to process.
     * Only one Intent is processed at a time, but the processing happens on a
     * worker thread that runs independently from other application logic.
     * So, if this code takes a long time, it will hold up other requests to
     * the same IntentService, but it will not hold up anything else.
     *
     * @param intent The value passed to {@link
     *               android.content.Context#startService(Intent)}.
     */
    protected abstract void onHandleIntent(Intent intent);

    /**
     * Mark an Intent as cancel intent. The Intent will not be placed in the queue;
     * instead, it will cause immediate cleaning of the queue
     * (unless you redefine {@link #onStart(Intent, int)} in a derived class).
     * @param intent to be modified
     * @return the original intent after modification
     */
    public static Intent markedAsCancelIntent(Intent intent) {
        intent.putExtra(CANCEL_MARK, true);
        return intent;
    }

    /**
     * Check if the intent has been marked as a cancel intent.
     * @param intent to be checked
     * @return true if it is a cancel intent
     */
    public static boolean isCancelIntent(Intent intent) {
        return intent.getBooleanExtra(CANCEL_MARK, false);
    }
}

我的服务类定义为:

public class MyService extends HangAroundIntentService {
    public MyService() {
        super("MyService");
    }
    public void onDestroy() {
        MyData.getMyData().shutdown();
        super.onDestroy();
    }
    // service-specific static methods not shown
}

未完待续...

于 2012-04-26T08:33:08.600 回答
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在实践中,事实证明某些原生库会泄漏资源;我必须重新启动进程(这并没有终止活动,而是重新创建了进程):

如何以编程方式“重启” android 应用程序?

只能希望没有库泄漏临时磁盘文件...

于 2013-01-15T08:35:45.093 回答