Java 使用MySql项目在Android中将JSON转换为字符串_Java_Android_Mysql_Database_Json

Java 使用MySql项目在Android中将JSON转换为字符串

java android mysql database json

Java 使用MySql项目在Android中将JSON转换为字符串,java,android,mysql,database,json,Java,Android,Mysql,Database,Json,我是Android新手，我正在尝试将我的Android应用程序连接到本地服务器phpmyadmin。我已经看过一些关于Android MySql通过PHP页面（使用JSON）交互的教程，但是我对输出有一个问题（例如，如何将从JSON获得的内容转换为字符串？）。为了让您更好地理解问题，以下是我的代码： JSONParser.java public class JSONParser { static InputStream is = null; static JSONObject jObj = n

我是Android新手，我正在尝试将我的Android应用程序连接到本地服务器phpmyadmin。我已经看过一些关于Android MySql通过PHP页面（使用JSON）交互的教程，但是我对输出有一个问题（例如，如何将从JSON获得的内容转换为字符串？）。为了让您更好地理解问题，以下是我的代码：

JSONParser.java

public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {

}

// function get json from url
// by making HTTP POST or GET method
public JSONObject makeHttpRequest(String url, String method,
        List<NameValuePair> params) {

    // Making HTTP request
    try {

        // check for request method
        if(method == "POST"){
            // request method is POST
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);
            httpPost.setEntity(new UrlEncodedFormEntity(params));

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        }else if(method == "GET"){
            // request method is GET
            DefaultHttpClient httpClient = new DefaultHttpClient();
            String paramString = URLEncodedUtils.format(params, "utf-8");
            url += "?" + paramString;
            HttpGet httpGet = new HttpGet(url);

            HttpResponse httpResponse = httpClient.execute(httpGet);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();
        }           


    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;

}
}

但现在如何保存在字符串中获得的标题和描述

非常感谢你的帮助

@赛蒙：这是LogCat

05-13 19:53:32.322: E/JSON Parser(10336): Error parsing data org.json.JSONException: Value <HTML><HEAD><TITLE> of type java.lang.String cannot be converted to JSONObject
05-13 19:53:32.322: D/AndroidRuntime(10336): Shutting down VM
05-13 19:53:32.322: W/dalvikvm(10336): threadid=1: thread exiting with uncaught exception (group=0x4001d578)
05-13 19:53:32.332: E/AndroidRuntime(10336): FATAL EXCEPTION: main
05-13 19:53:32.332: E/AndroidRuntime(10336): java.lang.RuntimeException: Unable to start activity ComponentInfo{package/package.MyActivity}: java.lang.NullPointerException
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1659)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1675)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread.access$1500(ActivityThread.java:121)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:943)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.os.Handler.dispatchMessage(Handler.java:99)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.os.Looper.loop(Looper.java:138)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread.main(ActivityThread.java:3701)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at java.lang.reflect.Method.invokeNative(Native Method)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at java.lang.reflect.Method.invoke(Method.java:507)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:878)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at dalvik.system.NativeStart.main(Native Method)
05-13 19:53:32.332: E/AndroidRuntime(10336): Caused by: java.lang.NullPointerException
05-13 19:53:32.332: E/AndroidRuntime(10336):    at package.MyActivity.onCreate(MyActivity.java:158)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1623)
05-13 19:53:32.332: E/AndroidRuntime(10336):    ... 11 more

你差点就成功了。实际上，您的

makeHttpRequest（）

方法返回从

PHP

脚本返回的

JSONObject

现在，您只需要解析

JSON

并从中检索和保存值

以下是作为伪代码的解决方案：

JSONParser parser = new JSONParser();
JSONObject obj = parser.makeHttpRequest("GET", <url>, <params>);
// getting data from JSON
String title = obj.getString("title");
String decription = obj.getString("description");

JSONParser=newjsonparser（）；
JSONObject obj=parser.makeHttpRequest（“GET”，）；
//从JSON获取数据
String title=obj.getString（“title”）；
字符串描述=obj.getString（“描述”）；

您面临的问题在哪里？首先获取json，然后在PHP端解析它，确保防止sql注入。使用mysql\u real\u escape\u字符串，无论您在哪里使用$\u GET或$\u POST等来获取将在SQL语句中使用的变量。感谢您的帮助！我尝试如下操作，但我设备中的应用程序崩溃。。我哪里做错了？（抱歉格式化…）公共类A扩展活动{..String ID；私有静态字符串url=“…”；JSONParser parser=new JSONParser（）；私有静态最终字符串标记_ID=“ID”；public void onCreate（Bundle s）{…try{List params=new ArrayList（）；params.add（new BasicNameValuePair（“ID”，ID））；JSONObject obj=parser.makeHttpRequest（url，“GET”，params）；String title=obj.getString（“title”）；String description=obj.getString（“description”）；}catch（JSONException e）{e.printStackTrace（）；}}..}@kareth将完整的日志添加到您的问题中。谢谢，我已经发布了日志猫@kareth您没有有效的

JSON

，请查看logcat，您首先得到的

JSONException

可能会导致

NullPointerException

。

05-13 19:53:32.322: E/JSON Parser(10336): Error parsing data org.json.JSONException: Value <HTML><HEAD><TITLE> of type java.lang.String cannot be converted to JSONObject
05-13 19:53:32.322: D/AndroidRuntime(10336): Shutting down VM
05-13 19:53:32.322: W/dalvikvm(10336): threadid=1: thread exiting with uncaught exception (group=0x4001d578)
05-13 19:53:32.332: E/AndroidRuntime(10336): FATAL EXCEPTION: main
05-13 19:53:32.332: E/AndroidRuntime(10336): java.lang.RuntimeException: Unable to start activity ComponentInfo{package/package.MyActivity}: java.lang.NullPointerException
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1659)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1675)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread.access$1500(ActivityThread.java:121)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:943)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.os.Handler.dispatchMessage(Handler.java:99)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.os.Looper.loop(Looper.java:138)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread.main(ActivityThread.java:3701)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at java.lang.reflect.Method.invokeNative(Native Method)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at java.lang.reflect.Method.invoke(Method.java:507)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:878)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at dalvik.system.NativeStart.main(Native Method)
05-13 19:53:32.332: E/AndroidRuntime(10336): Caused by: java.lang.NullPointerException
05-13 19:53:32.332: E/AndroidRuntime(10336):    at package.MyActivity.onCreate(MyActivity.java:158)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-13 19:53:32.332: E/AndroidRuntime(10336):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1623)
05-13 19:53:32.332: E/AndroidRuntime(10336):    ... 11 more

String title = obj.getString("title");

JSONParser parser = new JSONParser();
JSONObject obj = parser.makeHttpRequest("GET", <url>, <params>);
// getting data from JSON
String title = obj.getString("title");
String decription = obj.getString("description");