如何正确实现runOnUiThread Android

Question

我需要使用runOnUiThread来更新UI中的TextView，同时在从WebService获取一些字符串的工作线程中更新TextView。我看了一些其他的帖子，并试图实现提供的解决方案，但当我启动我的应用程序，它崩溃。我不太熟悉这个方法，所以我需要一些方向，如何解决这个问题。

Activity updateUI;

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

    updateUI = this;

    itemList = new ArrayList<>();

    new GetItemAvailability().execute();

}

@Override
    public Void doInBackground(Void... arg0) {
        HttpHandler handler = new HttpHandler();

        String JSON_DATA = handler.makeServiceCall(url);

        Log.e(TAG, "Response from url: " + JSON_DATA);

        if (JSON_DATA != null) {
            JSON_DATA = JSON_DATA.substring(JSON_DATA.indexOf('{'),JSON_DATA.lastIndexOf('}')+1);
            Log.e(TAG, "Substring of response: " + JSON_DATA);
            try {
                JSONObject reader = new JSONObject(JSON_DATA);

                JSONObject availability = reader.getJSONObject("availability");

                final String availableQuantity = availability.getString("availableQuantity");
                final String defaultBranch = availability.getString("defaultBranch");
                final String defaultInventoryBranch = availability.getString("defaultInventoryBranch");
                final String inventoryBranch = availability.getString("inventoryBranch");
                final String footage = availability.getString("footage");
                final String anticipatedStockDate = availability.getString("anticipatedStockDate");
                final String discontinuedItemFlag = availability.getString("discontinuedItemFlag");
                final String mdc = availability.getString("mdc");
                final String mdcquantity = availability.getString("mdcquantity");

                HashMap<String, String> item = new HashMap<>();

                item.put("availableQuantity", availableQuantity);
                item.put("defaultBranch", defaultBranch);
                item.put("defaultInventoryBranch", defaultInventoryBranch);
                item.put("inventoryBranch", inventoryBranch);
                item.put("footage", footage);
                item.put("anticipatedStockDate", anticipatedStockDate);
                item.put("discontinuedItemFlag", discontinuedItemFlag);
                item.put("mdc", mdc);
                item.put("mdcquantity", mdcquantity);

                itemList.add(item);

                updateUI.runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        tvAvailableQuantity.setText(availableQuantity);
                        tvDefaultBranch.setText(defaultBranch);
                        tvDefaultInventoryBranch.setText(defaultInventoryBranch);
                        tvInventoryBranch.setText(inventoryBranch);
                        tvFootage.setText(footage);
                        tvAnticipatedStockDate.setText(anticipatedStockDate);
                        tvDiscontinuedItemFlag.setText(discontinuedItemFlag);
                        tvMdc.setText(mdc);
                        tvMdcquantity.setText(mdcquantity);
                    }
                });

            }

Answer 1

您对runOnUiThread（）的实现是正确的。您向它传递一个在UI线程上运行的runnable。

但是，在您的情况下，如果将AsyncTask的结果类型更改为String，我认为这甚至没有必要，您可以简单地从doInBackground()方法返回json_data并将其余代码移到onPostExecute()中，该代码无论如何都运行在UI线程上。