Android runOnUiThread 以显示进度对话框并填充视图

Question

我通常在 .Net 上工作，但我需要开发一个 Android 应用程序。所以我是Android的新手，提前为错误道歉！ :)

这是我的故事， 我正在填充一个客户列表（在代码后面创建 ui 元素），单击按钮即可查看。我正在这样做，从数据库中提取数据。所以提取数据和创建视图需要一些时间。我想做的是在填充客户列表时显示进度对话框。目前我可以做到 运行。但问题是它没有立即显示进度对话框，然后同时显示客户列表和进度对话框。

这是我的按钮点击；

public void ShowCustomers(View view){
        final ProgressDialog dialog = new ProgressDialog(MainActivity.this);
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                dialog.setTitle("Title");
                dialog.setMessage("Loading...");
                if(!dialog.isShowing()){
                    dialog.show();
                }
            }
        });
        new Thread() {
            public void run() {
                try{
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            PopulateRecentGuests(); //Creates customer list dynamically
                            dialog.dismiss();
                        }
                    });
                } catch (Exception e) {
                    Log.e("tag", e.getMessage());
                }
            }
        }.start();
    }

并填充客户；

public void PopulateRecentGuests(){
        LinearLayout customers = (LinearLayout)findViewById(R.id.customers);
        String query = "SELECT * from Table";
        ModelCustomer customerModel = new ModelCustomer();
        ArrayList<HashMap<String, String>> recentGuests = customerModel.RetrievingQuery(query);
        customersCount = recentGuests.size();
        Context context = getApplicationContext();
        if(customersCount < 1)
            Toast.makeText(context, "There is no available customer in database!", Toast.LENGTH_LONG);
        else if(!recentGuests.get(0).containsKey("err")) {
            for(int i = 0; i < recentGuests.size(); i++){
                HashMap<String, String> guest = recentGuests.get(i);
                Button button = new Button(context);
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                params.setMargins(0,5,0,5);
                button.setLayoutParams(params);
                button.setWidth(800);
                button.setHeight(93);
                button.setTag(guest.get("id"));
                button.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        System.out.println("New button clicked! ID: " + v.getTag());
                        Intent intent = new Intent(getApplicationContext(), ProductPageActivity.class);
                        intent.putExtra("CustomerID", v.getTag().toString());
                        startActivity(intent);
                    }
                });
                button.setBackgroundColor(Color.parseColor("#EFEFEF"));
                button.setText(guest.get("FirstName") + " " + guest.get("LastName") + "             " + guest.get("GuideName"));
                button.setTextColor(Color.BLACK);
                button.setTextSize(20);
                button.setEnabled(false);
                customers.addView(button); // customers is a linear layout and button is being added to customers
                Button guest_list_btn = (Button)findViewById(R.id.guest_list_btn);
                guest_list_btn.setEnabled(true);
            }
        }
        else{
            CharSequence text = recentGuests.get(0).get("err");
            int duration = Toast.LENGTH_LONG;
            Toast toast = Toast.makeText(context, text, duration);
            toast.show();
        }

        Button guest_list_btn = (Button)findViewById(R.id.guest_list_btn);
        Button guest_list_close_btn = (Button)findViewById(R.id.guest_list_close_btn);

        customers.setVisibility(View.VISIBLE);
        AnimationSet aset = new AnimationSet(true);
        aset.setFillEnabled(true);
        aset.setInterpolator(new LinearInterpolator());

        AlphaAnimation alpha = new AlphaAnimation(0.0F, 1.0F);
        alpha.setDuration(400);
        aset.addAnimation(alpha);

        TranslateAnimation trans = new TranslateAnimation(200, 0, 0, 0);
        trans.setDuration(400);
        aset.addAnimation(trans);
        customers.startAnimation(aset);
        guest_list_btn.setEnabled(false);
        guest_list_close_btn.setEnabled(true);
        for(int i = 0; i < customers.getChildCount(); i++){
            View child = customers.getChildAt(i);
            child.setEnabled(true);
        }

    }

经过我的研究，我了解到运行onuithread是在looper之后调用的。我的问题是如何立即显示进度对话框然后填充客户列表（创建 ui 元素）。顺便说一下，我首先尝试使用 asynctask 来做到这一点，但我做不到。

比提前！

Answer 1

But the problem is it doesn't show the progress dialog immediately, then customerlist and progress dialog are displayed at the same time.

那是因为您在 UI 主线程上进行了长时间操作（并按顺序关闭了对话框）。相反，您应该将检索数据（这需要时间）和构建视图（以及关闭对话框）分开。

//...
new Thread() {
            public void run() {
                // do the long operation on this thread
                final ArrayList<HashMap<String, String>> recentGuests = customerModel.RetrievingQuery(query);
                // after retrieving the data then use it to build the views and close the dialog on the main UI thread
                try{
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            // remove the retrieving of data from this method and let it just build the views
                            PopulateRecentGuests(recentGuests); 
                            dialog.dismiss();
                        }
                    });
                } catch (Exception e) {
                    Log.e("tag", e.getMessage());
                }
            }
        }.start();