java - 自动从数据库中获取URL

Question

当我点击按钮 btnDelete 时，我试图自动从我的在线数据库表中获取一个 URL。问题是它从数据库返回正确的值，但是当尝试将它与:

Uri uri = Uri.parse(TAG_url);
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);

它说“不幸的是，对数据库的访问已停止。”

当我从 TAG_url 创建一个 Log.d() 时，它只返回“URL”，但是当我使用

txtDesc.setText(product.getString(TAG_url));

它正确显示来自数据库的链接。

03-14 11:50:18.169: E/Trace(5227): error opening trace file: No such file or directory (2)
03-14 11:50:31.499: E/AndroidRuntime(5227): FATAL EXCEPTION: main
03-14 11:50:31.499: E/AndroidRuntime(5227): java.lang.NullPointerException: uriString
03-14 11:50:31.499: E/AndroidRuntime(5227):     at android.net.Uri$StringUri.<init>(Uri.java:464)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at android.net.Uri$StringUri.<init>(Uri.java:454)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at android.net.Uri.parse(Uri.java:426)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at com.example.androidhive.EditProductActivity1$2.onClick(EditProductActivity1.java:106)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at android.view.View.performClick(View.java:4084)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at android.view.View$PerformClick.run(View.java:16966)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at android.os.Handler.handleCallback(Handler.java:615)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at android.os.Handler.dispatchMessage(Handler.java:92)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at android.os.Looper.loop(Looper.java:137)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at android.app.ActivityThread.main(ActivityThread.java:4745)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at java.lang.reflect.Method.invokeNative(Native Method)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at java.lang.reflect.Method.invoke(Method.java:511)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-14 11:50:31.499: E/AndroidRuntime(5227):     at dalvik.system.NativeStart.main(Native Method)
03-14 11:50:44.299: E/Trace(5251): error opening trace file: No such file or directory (2)

有人能帮帮我吗？

package com.example.androidhive;

import java.util.ArrayList;
import java.util.List;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class EditProductActivity extends Activity {

    EditText txtName;
    EditText txtPrice;
    EditText txtDesc;
    EditText txtimg;
    EditText txtCreatedAt;
    Button btnSave;
    Button btnDelete;
    Button btnvideo;

    String pid;
    String url;

    // Progress Dialog
    private ProgressDialog pDialog;

    // JSON parser class
    JSONParser jsonParser = new JSONParser();

    // single product url
    private static final String url_product_detials = "http://10.0.2.2/android_connect/get_product_details.php";

    // url to update product
    private static final String url_update_product = "http://10.0.2.2/android_connect/update_product.php";

    // url to delete product
    private static final String url_delete_product = "http://10.0.2.2/android_connect/delete_product.php";

    // JSON Node names
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_PRODUCT = "product";
    private static final String TAG_PID = "pid";
    private static final String TAG_NAME = "name";
    private static final String TAG_PRICE = "price";
    private static final String TAG_DESCRIPTION = "description";
    private static final String TAG_img = "img";
    private static final String TAG_url = "url";

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

        // save button
        btnSave = (Button) findViewById(R.id.btnSave);
        btnDelete = (Button) findViewById(R.id.btnDelete);

        // getting product details from intent
        Intent i = getIntent();

        // getting product id (pid) from intent
        pid = i.getStringExtra(TAG_PID);

        // Getting complete product details in background thread
        new GetProductDetails().execute();

        // save button click event
        btnSave.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // starting background task to update product
                new SaveProductDetails().execute();
            }
        });

        // Delete button click event
        btnDelete.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                // deleting product in background thread
                Log.v(TAG_url, "index=");
                Uri uri = Uri.parse(TAG_url);
                Intent intent = new Intent(Intent.ACTION_VIEW, uri);
                startActivity(intent);

            }
        });
    }

    /**
    * Background Async Task to Get complete product details
    * */
    class GetProductDetails extends AsyncTask<String, String, String> {

        /**
        * Before starting background thread Show Progress Dialog
        * */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(EditProductActivity.this);
            pDialog.setMessage("Loading movies details. Please wait...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();
        }

        /**
        * Getting product details in background thread
        * */
        protected String doInBackground(String... params) {
            // updating UI from Background Thread
            runOnUiThread(new Runnable() {

                public void run() {
                    // Check for success tag
                    int success;
                    try {
                        // Building Parameters
                        List<NameValuePair> params = new ArrayList<NameValuePair>();
                        params.add(new BasicNameValuePair("pid", pid));

                        // getting product details by making HTTP request
                        // Note that product details url will use GET request
                        JSONObject json = jsonParser.makeHttpRequest(
                                url_product_detials, "GET", params);

                        // check your log for json response
                        Log.d("Single Product Details", json.toString());

                        // json success tag
                        success = json.getInt(TAG_SUCCESS);
                        if (success == 1) {
                            // successfully received product details
                            JSONArray productObj = json
                                    .getJSONArray(TAG_PRODUCT); // JSON Array

                            // get first product object from JSON Array
                            JSONObject product = productObj.getJSONObject(0);

                            // product with this pid found
                            // Edit Text
                            url = TAG_url;
                            Log.v(url, "index=");
                            txtName = (EditText) findViewById(R.id.inputName);
                            txtPrice = (EditText) findViewById(R.id.inputPrice);
                            txtDesc = (EditText) findViewById(R.id.inputDesc);
                            // txtimg = (EditText) findViewById(R.id.inputimg);

                            // display product data in EditText
                            txtName.setText(product.getString(TAG_NAME));
                            txtPrice.setText(product.getString(TAG_PRICE));
                            txtDesc.setText(product.getString(TAG_url));
                            txtimg.setText(product.getString(TAG_img));
                        } else {
                            // product with pid not found
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }

                private String getText(String string) {
                    // TODO Auto-generated method stub
                    return null;
                }
            });

            return null;
        }

        /**
        * After completing background task Dismiss the progress dialog
        * **/
        protected void onPostExecute(String file_url) {
            // dismiss the dialog once got all details
            pDialog.dismiss();
        }
    }

    /**
    * Background Async Task to Save product Details
    * */
    class SaveProductDetails extends AsyncTask<String, String, String> {

        /**
        * Before starting background thread Show Progress Dialog
        * */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(EditProductActivity.this);
            pDialog.setMessage("Saving product ...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();
        }

        /**
        * Saving product
        * */
        protected String doInBackground(String... args) {
            // getting updated data from EditTexts
            String name = txtName.getText().toString();
            String price = txtPrice.getText().toString();
            String description = txtDesc.getText().toString();
            String img = txtimg.getText().toString();

            // Building Parameters
            List<NameValuePair> params = new ArrayList<NameValuePair>();
            params.add(new BasicNameValuePair(TAG_PID, pid));
            params.add(new BasicNameValuePair(TAG_NAME, name));
            params.add(new BasicNameValuePair(TAG_PRICE, price));
            params.add(new BasicNameValuePair(TAG_DESCRIPTION, description));
            params.add(new BasicNameValuePair(TAG_img, img));
            params.add(new BasicNameValuePair(TAG_url, url));

            // sending modified data through http request
            // Notice that update product url accepts POST method
            JSONObject json = jsonParser.makeHttpRequest(url_update_product,
                    "POST", params);

            // check json success tag
            try {
                int success = json.getInt(TAG_SUCCESS);

                if (success == 1) {
                    // successfully updated
                    Intent i = getIntent();
                    // send result code 100 to notify about product update
                    setResult(100, i);
                    finish();
                } else {
                    // failed to update product
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

            return null;
        }

        /**
        * After completing background task Dismiss the progress dialog
        * **/
        protected void onPostExecute(String file_url) {
            // dismiss the dialog once product uupdated
            pDialog.dismiss();
        }
    }
}

Answer 1

在我看来，var TAG_url 旨在仅用作描述符，而不是用作可变对象。首先，您有: private static final String TAG_url = "url"; 定义为节点名称。将其用于 txtDesc.setText(product.getString(TAG_url)); 是可行的，因为您正在检索与节点“url”关联的数据(TAG_url 包含的内容).在这种情况下，数据不在 TAG_url var 中，而是使用 TAG_url 作为查找数据的键。

任何对 TAG_url 的日志引用都将返回其内容:url。出于同样的原因，使用 TAG_url 的解析调用也将使用它的内容。因此，Uri uri = Uri.parse(TAG_url); 实际上是在调用 Uri uri = Uri.parse("url"); - 所以是错误。

您应该将解析调用中的 TAG_url 替换为包含您打算调用的实际 url 的 var。在你的数据库调用期间，你应该将该 url 存储在一个单独的 var 中，然后解析它。

编辑:

在不知道您的 JSON 或其他数据的结构的情况下，我无法确定。但作为示例，我们假设通过调用 product.getString(TAG_url) 从数据库返回的数据是您要发送到解析器的数据。 (我假设因为你提到当通过 txtDesc.setText(product.getString(TAG_url)); 调用时，数据已正确设置到 TextView txtDesc。)

鉴于此，您可以在类的顶部创建一个字段 String incomingURL;，并分配数据库调用的结果，如 incomingURL = product.getString(TAG_url);。然后，您可以使用新字段设置 TextView，例如 txtDesc.setText(incomingURL);。

然后，使用该变量进行解析:Uri uri = Uri.parse(incomingURL); 这将从数据库调用中获取数据，并将其放入解析器中。请记住，如果按钮在数据库调用完成之前可点击，则需要检查 incomingURL 是否为 null。