如何在进行新活动之前杀死线程和处理程序

Question

大家好——这段代码在我试图清理处理程序时可能有点混乱，因为我一直在试图追踪崩溃发生的位置......

我有一个对话框活动，它显示了一个密码条目，其中一个进度条由线程和处理程序动画...

似乎当我尝试查看进度条是否已完成并尝试终止线程时，当我尝试进行新活动时，我这样做的方式会搞砸一些事情 - 即在调用函数并且没有任何东西可以返回 to 或其他东西的方式......

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

Thread.stop is deprecated call，您应该改用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
}

Thread.Interrupt 将在下次您的线程阻塞或休眠并且您已经在线程主体中处理时导致ThreadInterruptedException，这很好。此外，您可能希望包含一个 volatile 标志，它允许您在线程未阻塞或休眠时停止线程，但这是可选的。

Answer 2

您可以考虑使用 AsyncTask 实例而不是可运行对象和处理程序。

如果您需要取消 AsycnTask 实例，只需在您的 AsyncTask 对象引用上调用 .cancel(true)。这将同时处理后台方法 (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 中，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
        }
    }

}