从数据库中检索数据时如何使用线程

Question

所以这是我试图用线程实现的方法，但是在运行它时它一直在崩溃，我不知道为什么.. logcat 不会像当某些东西崩溃时那样向我显示错误，这让我非常困惑。 .

所以基本上我在这里尝试做的是开始我的活动，当用户查看活动时，它开始在后台填充列表，如果这有助于解释我试图完成的事情。

Handler handler = new Handler(){
    @Override
    public void handleMessage(Message msg) {
        populateExerListView(exercises);
    }
};

public void loadDataFromDatabase(){
    Runnable r = new Runnable() {
        @Override
        public void run() {
            exercises = dbh.getAllExercises(bodypart_chosen);
            handler.sendEmptyMessage(0);
        }
    };

public void populateExerListView(final ArrayList<AdapterExercisesList.Exercise> exercises){

    ListAdapter edsAdapter = new AdapterExercisesList(this, exercises);
    exerciseListView = (ListView) findViewById(R.id.exerciseListView);

    exerciseListView.setAdapter(edsAdapter);

    exerciseListView.setOnItemClickListener(
            new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    int pos = (Integer) view.getTag();
                    //gets the bodypart by passing in the pos
                    String exercise_chosen = exercises.get(pos).get_exerciseName();

                    Calendar c = Calendar.getInstance();
                    SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
                    String formattedDate = df.format(c.getTime());
                    exerciseClicked(exercise_chosen, formattedDate);
                }
            }
    );
}

Answer 1

你定义了可运行但你从不将它传递给线程，

你需要改变这个：

public void loadDataFromDatabase(){
    Runnable r = new Runnable() {
        @Override
        public void run() {
            exercises = dbh.getAllExercises(bodypart_chosen);
            handler.sendEmptyMessage(0);
        }
    };

对此：

public void loadDataFromDatabase(){

    new Thread(new Runnable() {
        @Override
        public void run() {
            exercises = dbh.getAllExercises(bodypart_chosen);
            handler.sendEmptyMessage(0);
        }
    }).start();

}//end method