如何解决Android Java中的并发问题？

Question

将锁定设置为等待5秒后，getArt（）线程将锁定，在5秒钟后恢复线程并返回响应。但是设置了锁定后，线程将终止。

如何防止线程终止，并在锁等待时强制其继续获取响应，并且在返回响应之后，它应该为mLock.notifyAll（）;。恢复一切，我的代码正常工作。

我之前没有在while循环中尝试过它，并且在其他方​​法将该值用作null后，它确实返回了响应。

请帮助。

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：我使用辅助线程读取值（而不是像过去那样使用UI线程）自行解决。感谢您的投票，并感谢任何尝试提供帮助的人。

解决方案：

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

您不应在同步块之外使用notifyAll方法。否则，将引发异常java.lang.IllegalMonitorStateException。

使用wait方法时，将释放锁变量，并且内部线程将能够使用此监视器。