java - 如何解决 Android Java 中的并发问题？

Question

当锁定设置为等待 5 秒时，getArt() 线程锁定，5 秒后线程恢复并返回响应。但是线程在设置锁后终止。

如何防止线程被终止并强制它在锁等待期间继续获取响应，并且在响应返回后，它应该 mLock.notifyAll();恢复一切，我的代码工作。

我之前在没有while循环的情况下尝试过，它确实在其他方法将值用作null后返回了响应。

请帮忙。

private void setArt(String imgArt){
    this.imgArt = imgArt;
}

private void setDone(){
    this.done = true;
}

private void getArt(){
    mLock = new Object();

    Thread thread = new Thread() {
        @Override
        public void run() {
            try {
                StringRequest stringRequest = new StringRequest(Request.Method.POST, String.format("%sFetchMP3Image.php", Station_Util.URL),
                        new Response.Listener<String>() {
                            @Override
                            public void onResponse(String response) {
                                try {
                                    System.out.println("Response received.");
                                    JSONObject Response = new JSONObject(response);
                                    String Status = Response.getString("Response");
                                    if (Status.equals("Success")) {
                                        JSONObject MP3File = Response.getJSONObject("MP3");
                                        String ImageURL = MP3File.getString("ImageURL");
                                        setArt(ImageURL);
                                        mLock.notifyAll();
                                        setDone();
                                    }
                                } catch (Exception e) {

                                }
                            }
                        },
                        new Response.ErrorListener() {
                            @Override
                            public void onErrorResponse(VolleyError error) {

                            }
                        }) {
                    @Override
                    protected Map<String, String> getParams() {
                        Map<String, String> params = new HashMap<String, String>();
                        params.put("MP3Name", "687956770_1134920615_1196563259.mp3");
                        return params;
                    }

                };

                Volley.newRequestQueue(My_Downloads.this).add(stringRequest);
            } catch (Exception e) {
            }
        }
    };
    thread.start();

    try {
        while(!this.done) {
            synchronized (mLock) {
                System.out.println("Thread Alive Before: " + thread.isAlive());
                System.out.println("Thread Alive Before: " + thread.getState());
                System.out.println("Thread Alive Before: " + thread.isInterrupted());
                mLock.wait(5000);
                System.out.println("Thread Alive After: " + thread.isAlive());
                System.out.println("Thread Alive After: " + thread.getState());
                System.out.println("Thread Alive After: " + thread.isInterrupted());
            }
        }
        SetList();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

编辑 1:我自己解决了这个问题，使用辅助线程读取值，而不是像以前那样使用 UI 线程。感谢您的赞成票和任何试图提供帮助的人。

解决方法:

private void setArt(String imgArt){
    this.imgArt = imgArt;
}

private void setDone(){
    this.done = true;
}

private boolean getDone()
{
    return this.done;
}

private void setListed(){
    this.listed = true;
}

private boolean getListed(){
    return this.listed;
}

private void getArt(){
    mLock = new Object();

    final Thread thread = new Thread() {
        @Override
        public void run() {
            try {
                synchronized (mLock) {
                    StringRequest stringRequest = new StringRequest(Request.Method.POST, String.format("%sFetchMP3Image.php", Station_Util.URL),
                            new Response.Listener<String>() {
                                @Override
                                public void onResponse(String response) {
                                    try {
                                        System.out.println("Response received: " + response);
                                        JSONObject Response = new JSONObject(response);
                                        String Status = Response.getString("Response");
                                        if (Status.equals("Success")) {
                                            System.out.println("Status: " + Status);
                                            JSONObject MP3File = Response.getJSONObject("MP3");
                                            String ImageURL = MP3File.getString("ImageURL");
                                            System.out.println("ImageURL: " + ImageURL);
                                            setArt(ImageURL);
                                            //mLock.notifyAll();
                                            setDone();
                                            System.out.println("Done in API thread: " + getDone());
                                        }
                                    } catch (Exception e) {

                                    }
                                }
                            },
                            new Response.ErrorListener() {
                                @Override
                                public void onErrorResponse(VolleyError error) {

                                }
                            }) {
                        @Override
                        protected Map<String, String> getParams() {
                            Map<String, String> params = new HashMap<String, String>();
                            params.put("MP3Name", "687956770_1134920615_1196563259.mp3");
                            return params;
                        }

                    };

                    Volley.newRequestQueue(My_Downloads.this).add(stringRequest);
                }
            } catch(Exception e){
            }
        }
    };
    thread.start();

    Thread thread2 = new Thread() {
        @Override
        public void run() {
            try {
                while (!getDone()) {
                    synchronized (mLock) {
                        mLock.wait(250);
                        System.out.println("API Thread Alive: " + thread.isAlive());
                        System.out.println("Done in Reading Thread: " + getDone());

                        new Handler(Looper.getMainLooper()).post(new Runnable() {
                            @Override
                            public void run() {
                                System.out.println("UI Thread Done: " + getDone());
                                if (getDone()){
                                    setListed();
                                    SetList();
                                }
                            }
                        });
                    }
                }

                if (getDone() && !getListed()) {
                    setListed();
                    SetList();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    };
    thread2.start();
}

Answer 1

您不应在同步块(synchronized block)外使用 notifyAll 方法。否则，异常 java.lang.IllegalMonitorStateException将被抛出。

当您使用wait 方法时，锁变量将被释放，内部线程将能够使用此监视器。