如何在进入新活动之前终止线程和处理程序

Question

大家好 - 在我尝试清理处理程序时，这段代码可能有点混乱，因为我一直在尝试追踪崩溃发生的位置...

我有一个显示密码的对话框活动带有由线程和处理程序动画的进度条的条目...

似乎当我试图查看进度条是否完成并试图终止线程时，我这样做的方式正在搞乱一些东西，当我尝试去一个新的活动 - 即以某种方式调用一个函数并且没有任何东西可以返回到或其他东西......

public class RMO_Dialog extends Activity {
    private ProgressBar progbar;
    private Button dialogOK;
    private EditText dialogPass;
    private SharedPreferences prefs;
    private String pass;
    private int increment=10;
    private Thread background;

    private Boolean commCalled=false;

    public void callCommunications(){
        progbar.setVisibility(0);
        progbar.setProgress(0);
        background.stop();
        Toast.makeText(getApplicationContext(), "Call communication should happen once.", Toast.LENGTH_LONG).show();
//      Intent i = new Intent();
//      i.setClass(RMO_Dialog.this, RMO_Comm.class);
//      i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
//      startActivity(i);
//          finish();
    }

    public void buzzUser(){

        Vibrator v = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
        int dot = 200;
        int dash = 500;
        int short_gap = 200;
        int medium_gap = 500;
        int long_gap = 1000;
        long[] pattern = {0,dot, short_gap, dot, short_gap, dot, medium_gap, dash, short_gap, dash, short_gap, dash, medium_gap, dot, short_gap, 
                dot, short_gap, dot, long_gap};

        v.vibrate(pattern, -1);


    }

    public void killCountdown(){
        progbar.setVisibility(0);
        progbar.setProgress(0);
        background.stop();
    }

    @Override
    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.dialogpassword);

        buzzUser();

        prefs = this.getSharedPreferences("RMO", MODE_WORLD_READABLE);
        pass = prefs.getString("password", "");

        dialogOK = (Button) findViewById(R.id.dialogOK);
        dialogPass = (EditText) findViewById(R.id.dialogPass);
        progbar = (ProgressBar) findViewById(R.id.progress);

        progbar.setProgress(0);

        background = new Thread(new Runnable(){
            @Override
            public void run() {
                try{
                    while(progbar.getProgress()<=progbar.getMax()){
                        Thread.sleep(300);
                        progressHandler.sendMessage(progressHandler.obtainMessage());
                    }
                }catch(java.lang.InterruptedException e){
                    Toast.makeText(getApplicationContext(), "Error thrown.", Toast.LENGTH_LONG).show();
                }

            }

        });
        background.start();

        dialogOK.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(dialogPass.getText().toString().equals(pass.toString())){
                    killCountdown();
                    Toast.makeText(getApplicationContext(), "Guardian Angel next alert has been disengaged.", Toast.LENGTH_LONG).show();
                    Intent intent = new Intent();
                    intent.setClass(RMO_Dialog.this, RMO.class);
                    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    startActivity(intent);
                    finish();
                }else{
                    callCommunications();
                }
            }
        });



    }

    Handler progressHandler = new Handler(){
        public void handleMessage(Message msg){
            progbar.incrementProgressBy(increment);
            if(progbar.getProgress()==progbar.getMax()){
                Toast.makeText(getApplicationContext(), "commcalled: "+ commCalled, Toast.LENGTH_LONG).show();
                if(commCalled==false){
                    commCalled=true;
                    callCommunications();
                }

            }
        }
    };
}

Answer 1

您可以考虑使用 AsyncTask 实例一个可运行程序和一个处理程序。

如果您需要取消 AsycnTask 实例，只需在 AsyncTask 对象引用上调用 .cancel(true) 即可。这将处理后台方法 (doInBackground()) 和进度更新程序 (onProgressUpdate())。

我通常发现 AsyncTask 比尝试自己处理所有细节更容易使用。

因此，在 RMO_Dialog 内部，对您创建的扩展 AsyncTask 的类的实例使用调用 execute()。

public class RMO_Dialog extends Activity {

    ...
    // Get ref to your bg task for easily cancellation if needed
    PassWordEntry background = new PassWordEntry();
    // Start bg task
    background.execute([PARAMS]);
    ...
    // Cancel task
    background.cancel(true);
    ...

    // AsyncTask lets you encapsulate both your runnable and handler in it
    private static class PassWordEntry() extends AsyncTask<[PARAMS], [PROGRESS], [RESULT]> {
        protected [RESULT] doInBackground() {
            ... // Runnable stuff here
            return [RESULT];
        }

        protected void onProgressUpdate([PROGRESS]... progress) {
            ... // progressHandler stuff here
        }

        protected void onPostExecute([RESULT]) {           
            // Clean up return data when all done w BG here
        }
    }

}

Answer 2

Thread.stop 已弃用调用，而是应该使用 Thread.interrupt 方法。

public void killCountdown(int waitTime){
    progbar.setVisibility(0);
    progbar.setProgress(0);
    // deprecated: background.stop();
    background.interrupt(); // <-- OK
    background.join(waitTime); // optionally wait for the thread to exit
}

下次线程阻塞或睡眠时，Thread.Interrupt 将导致 ThreadInterruptedException，并且您已经在线程体中进行处理，所以这很好。此外，您可能需要包含一个 易失性 标志，该标志允许您在线程未阻塞或休眠时停止线程，但这是可选的。