Java JSON：从用户定义JSON函数获取空字符串

我第一次从

Json

函数中得到

null

字符串 我有两个类文件：

func.java

main.java

在

func.java中

code是

package com.example.json;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Random;
import android.content.Context;
import org.apache.http.Header;
import org.json.JSONException;
import org.json.JSONObject;

import com.loopj.android.http.AsyncHttpClient;
import com.loopj.android.http.AsyncHttpResponseHandler;

import android.widget.Toast;

public class func {
    public static String res = null;

    public static String jsonv(String url, Context c) {
        AsyncHttpClient client = new AsyncHttpClient();

        client.get(url, new AsyncHttpResponseHandler() {

            @Override
            public void onSuccess(int arg0, Header[] arg1, byte[] arg2) {

                try {
                    res = new String(arg2);
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    res = "error 1 ";
                }

                // Toast.makeText(getApplicationContext(), res,
                // Toast.LENGTH_LONG).show();
            }

            @Override
            public void onFailure(int arg0, Header[] arg1, byte[] arg2, Throwable arg3) {
                res = "error 2";
            }
        });
        return res;
    }
}

在func.java中，我编写了获取JSON字符串的代码，并且只希望它出现在函数中 然后在main.java中

public class main extends Activity {
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String getj = func.jsonv("192.168.71.1/json?app=1", getApplicationContext());
        Toast.makeText(getApplicationContext(), "json is" + getj, 1000).show();
    }
}

它给出了

null

，因为在应用程序启动时

json

仍在加载，所以当

json

成功加载时如何执行操作，我只希望它以函数形式出现，这样我就可以随时随地使用它

这是日志

06-21 14:10:01.193: I/BufferQueue(19206): [unnamed-19206-0](this:0x60e29008,id:0,api:0,p:-1,c:-1) BufferQueue
06-21 14:10:01.193: I/GLConsumer(19206): [void android::RingBuffer<TYPE>::resize(uint32_t, bool) [with TYPE = android::sp<android::BackupBuffer>; uint32_t = unsigned int]] 0x60e25e3c resize to 10 (force=true)
06-21 14:10:01.193: I/GLConsumer(19206): [void android::RingBuffer<TYPE>::resize(uint32_t, bool) [with TYPE = android::sp<android::BackupBuffer>; uint32_t = unsigned int]] 0x60e25e3c resize to 0 (force=false)
06-21 14:10:01.194: I/BufferQueue(19206): [unnamed-19206-0](this:0x60e29008,id:0,api:0,p:-1,c:19206) consumerConnect consumer=(19206:com.example.json) controlledByApp=true
06-21 14:10:01.194: I/BufferQueue(19206): [unnamed-19206-0](this:0x60e29008,id:0,api:0,p:-1,c:19206) setConsumerName: unnamed-19206-0
06-21 14:10:01.194: I/GLConsumer(19206): [unnamed-19206-0](this:0x60e29670,api:0) GLConsumer
06-21 14:10:01.194: I/GLConsumer(19206): [unnamed-19206-0](this:0x60e29670,api:0) detachFromContext
06-21 14:10:01.204: D/VelocityTracker(19206): Couldn't open '/dev/touch' (Permission denied)
06-21 14:10:01.204: D/VelocityTracker(19206): tpd read x fail: Bad file number
06-21 14:10:01.205: D/VelocityTracker(19206): tpd read y fail: Bad file number
06-21 14:10:01.205: D/WebViewCallback(19206): getVisitedHistory
06-21 14:10:01.219: D/dalvikvm(19206): threadid=15: interp stack at 0x6163b000
06-21 14:10:01.222: D/MediatekClassFactory(19206): createInstance(): Begin = 5611917
06-21 14:10:01.222: D/MediatekClassFactory(19206): create Instance with :  interface com.mediatek.common.telephony.IOnlyOwnerSimSupport
06-21 14:10:01.222: W/MediatekClassFactory(19206): Tablet not exist!, Get obj from default class
06-21 14:10:01.223: D/MediatekClassFactory(19206): create Instance from tablet library :  com.mediatek.tb.telephony.OnlyOwnerSimSupport
06-21 14:10:01.223: D/MediatekClassFactory(19206): createInstance(): End = 5611918
06-21 14:10:01.303: D/dalvikvm(19206): create interp thread : stack size=128KB
06-21 14:10:01.303: D/dalvikvm(19206): create new thread
06-21 14:10:01.304: D/dalvikvm(19206): new thread created
06-21 14:10:01.304: D/dalvikvm(19206): update thread list
06-21 14:10:01.304: D/dalvikvm(19206): threadid=16: interp stack at 0x61694000
06-21 14:10:01.304: D/dalvikvm(19206): threadid=16: created from interp
06-21 14:10:01.304: D/dalvikvm(19206): start new thread
06-21 14:10:01.304: D/dalvikvm(19206): threadid=16: notify debugger
06-21 14:10:01.304: D/dalvikvm(19206): threadid=16 (RefQueueWorker@org.apache.http.impl.conn.tsccm.ConnPoolByRoute@427f7c80): calling run()
06-21 14:10:01.309: I/System.out(19206): httpget:http://192.168.71.1/json/?app=0b52765ac1d697a37891605df3c27e0f
06-21 14:10:01.310: I/System.out(19206): http://192.168.71.1/json/?app=0b52765ac1d697a37891605df3c27e0f
06-21 14:10:01.310: D/dalvikvm(19206): create interp thread : stack size=128KB
06-21 14:10:01.310: D/dalvikvm(19206): create new thread
06-21 14:10:01.310: D/dalvikvm(19206): new thread created
06-21 14:10:01.310: D/dalvikvm(19206): update thread list
06-21 14:10:01.311: D/dalvikvm(19206): threadid=17: interp stack at 0x616b9000
06-21 14:10:01.311: D/dalvikvm(19206): threadid=17: created from interp
06-21 14:10:01.311: D/dalvikvm(19206): start new thread
06-21 14:10:01.311: D/dalvikvm(19206): threadid=17: notify debugger
06-21 14:10:01.311: D/dalvikvm(19206): threadid=17 (pool-1-thread-1): calling run()
06-21 14:10:01.317: I/System.out(19206): [socket][0] connection /192.168.71.1:80;LocalPort=56751(10000)
06-21 14:10:01.317: I/System.out(19206): [CDS]connect[/192.168.71.1:80] tm:10
06-21 14:10:01.317: D/Posix(19206): [Posix_connect Debug]Process com.example.json :80 
06-21 14:10:01.318: I/System.out(19206): [socket][/192.168.71.101:56751] connected
06-21 14:10:01.318: I/System.out(19206): [CDS]rx timeout:10000
06-21 14:10:01.319: I/System.out(19206): [CDS]SO_SND_TIMEOUT:0
06-21 14:10:01.320: D/ActivityThread(19206): ACT-AM_ON_RESUME_CALLED ActivityRecord{41f53428 token=android.os.BinderProxy@41f52b48 {com.example.json/com.example.json.MainActivity}}
06-21 14:10:01.321: I/System.out(19206): >doSendRequest
06-21 14:10:01.323: I/System.out(19206): <doSendRequest
06-21 14:10:01.323: V/PhoneWindow(19206): DecorView setVisiblity: visibility = 4 ,Parent =null, this =com.android.internal.policy.impl.PhoneWindow$DecorView{41f7b548 I.E..... R.....ID 0,0-0,0}
06-21 14:10:01.333: V/PhoneWindow(19206): DecorView setVisiblity: visibility = 0 ,Parent =ViewRoot{42821dd0 com.example.json/com.example.json.MainActivity,ident = 0}, this =com.android.internal.policy.impl.PhoneWindow$DecorView{41f7b548 V.E..... R.....ID 0,0-0,0}
06-21 14:10:01.333: D/ActivityThread(19206): ACT-LAUNCH_ACTIVITY handled : 0 / ActivityRecord{41f53428 token=android.os.BinderProxy@41f52b48 {com.example.json/com.example.json.MainActivity}}
06-21 14:10:01.371: E/(19206): appName=com.example.json, acAppName=/system/bin/surfaceflinger
06-21 14:10:01.371: E/(19206): 0
06-21 14:10:01.374: D/GraphicBuffer(19206): create handle(0x617e0348) (w:544, h:960, f:1)
06-21 14:10:01.378: I/MaliEGL(19206): [Mali]window_type=1, is_framebuffer=0, errnum = 0
06-21 14:10:01.378: I/MaliEGL(19206): [Mali]surface->num_buffers=4, surface->num_frames=3, win_min_undequeued=1
06-21 14:10:01.378: I/MaliEGL(19206): [Mali]max_allowed_dequeued_buffers=3
06-21 14:10:01.378: D/GraphicBuffer(19206): close handle(0x617e0348) (w:544 h:960 f:1)
06-21 14:10:01.380: I/(19206): [custom_prop]custom_get_string->module[browser],key[UAProfileURL]
06-21 14:10:01.380: I/(19206): [custom_prop]reset_parser->keep[0]
06-21 14:10:01.380: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.380: I/(19206): [custom_prop]reset_parser->keep[1]
06-21 14:10:01.380: D/GraphicBuffer(19206): create handle(0x617e2de8) (w:544, h:960, f:1)
06-21 14:10:01.382: D/OpenGLRenderer(19206): Enabling debug mode 0
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]reset_parser->keep[1]
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]reset_parser->keep[1]
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_PROP
06-21 14:10:01.382: I/(19206): [custom_prop]prop name:ro.build.version.release
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]reset_parser->keep[1]
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_PROP
06-21 14:10:01.382: I/(19206): [custom_prop]prop name:ro.build.version.release
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]reset_parser->keep[1]
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]reset_parser->keep[1]
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]reset_parser->keep[1]
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]reset_parser->keep[1]
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]reset_parser->keep[1]
06-21 14:10:01.382: I/(19206): [custom_prop]enter STATE_VALUE
06-21 14:10:01.382: I/(19206): [custom_prop]reset_parser->keep[1]
06-21 14:10:01.382: I/(19206): [custom_prop]reset_parser->keep[0]
06-21 14:10:01.383: D/GraphicBuffer(19206): create handle(0x617e1968) (w:768, h:768, f:1)
06-21 14:10:01.385: I/[MALI][Gralloc](19206): dlopen libsec_mem.so fail
06-21 14:10:01.386: D/OpenGLRenderer(19206): setViewport 540x960 <0x60e3c360>
06-21 14:10:01.387: I/BufferQueue(19206): [unnamed-19206-0](this:0x60e29008,id:0,api:0,p:-1,c:19206) setDefaultBufferSize: w=150, h=150
06-21 14:10:01.387: I/BufferQueue(19206): [unnamed-19206-0](this:0x60e29008,id:0,api:0,p:-1,c:19206) setDefaultBufferSize: w=150, h=150
06-21 14:10:01.403: V/InputMethodManager(19206): onWindowFocus: android.webkit.WebView{41f76e28 VFED..C. .F....ID 195,488-345,638 #7f0a0003 app:id/webView1} softInputMode=288 first=true flags=#1810100
06-21 14:10:01.404: V/InputMethodManager(19206): START INPUT: android.webkit.WebView{41f76e28 VFED..C. .F....ID 195,488-345,638 #7f0a0003 app:id/webView1} ic=com.android.org.chromium.content.browser.input.AdapterInputConnection@42835280 tba=android.view.inputmethod.EditorInfo@42835190 controlFlags=#105
06-21 14:10:01.415: W/AwContents(19206): nativeOnDraw failed; clearing to background color.
06-21 14:10:01.416: D/OpenGLRenderer(19206): prepareDirty (0.00, 0.00, 540.00, 960.00) opaque 1 <0x60e3c360>
06-21 14:10:01.463: D/OpenGLRenderer(19206): finish <0x60e3c360>
06-21 14:10:01.468: D/WebViewCallback(19206): onProgressChanged=0
06-21 14:10:01.471: V/AsyncHttpResponseHandler(19206): Progress 90 from 90 

06-21 14:10:01.193:I/BufferQueue（19206）：[unnamed-19206-0]（此代码：0x60e29008，id:0，api:0，p:-1，c:-1）BufferQueue
I/GLConsumer（19206）：[void android:：RingBuffer:：resize（uint32_t，bool）[with TYPE=android:：sp；uint32_t=unsigned int]]0x60e25e3c将大小调整为10（force=true）
I/GLConsumer（19206）：[void android:：RingBuffer:：resize（uint32_t，bool）[with TYPE=android:：sp；uint32_t=unsigned int]]0x60e25e3c将大小调整为0（force=false）
06-21 14:10:01.194:I/BufferQueue（19206）：[unnamed-19206-0]（this:0x60e29008，id:0，api:0，p:-1，c:19206）consumerConnect consumer=（19206:com.example.json）controlledByApp=true
06-21 14:10:01.194:I/BufferQueue（19206）：[unnamed-19206-0]（此代码：0x60e29008，id:0，api:0，p:-1，c:19206）setConsumerName:unnamed-19206-0
06-21 14:10:01.194:I/GLConsumer（19206）：[unnamed-19206-0]（此代码：0x60e29670，api:0）GLConsumer
06-21 14:10:01.194:I/GLConsumer（19206）：[unnamed-19206-0]（此代码：0x60e29670，api:0）脱离上下文
06-21 14:10:01.204:D/VelocityTracker（19206）：无法打开“/dev/touch”（权限被拒绝）
06-21 14:10:01.204:D/VelocityTracker（19206）：tpd读取x失败：错误的文件号
06-21 14:10:01.205:D/VelocityTracker（19206）：tpd读取y失败：错误的文件号
06-21 14:10:01.205:D/WebViewCallback（19206）：getVisitedHistory
06-21 14:10:01.219:D/dalvikvm（19206）：threadid=15:0x6163b000处的内部堆栈
06-21 14:10:01.222:D/MediatekClassFactory（19206）：createInstance（）：Begin=5611917
06-21 14:10:01.222:D/MediatekClassFactory（19206）：使用接口com.mediatek.common.telephony.IOnlyOwnerSimSupport创建实例
06-21 14:10:01.222:W/MediatekClassFactory（19206）：平板电脑不存在！，从默认类获取obj
06-21 14:10:01.223:D/MediatekClassFactory（19206）：从平板电脑库创建实例：com.mediatek.tb.telephony.OnlyOwnerSimSupport
06-21 14:10:01.223:D/MediatekClassFactory（19206）：createInstance（）：End=5611918
06-21 14:10:01.303:D/dalvikvm（19206）：创建内部线程：堆栈大小=128KB
06-21 14:10:01.303:D/dalvikvm（19206）：创建新线程
06-21 14:10:01.304:D/dalvikvm（19206）：创建新线程
06-21 14:10:01.304:D/dalvikvm（19206）：更新线程列表
06-21 14:10:01.304:D/dalvikvm（19206）：threadid=16:0x61694000处的内部堆栈
06-21 14:10:01.304:D/dalvikvm（19206）：threadid=16：从interp创建
06-21 14:10:01.304:D/dalvikvm（19206）：启动新线程
06-21 14:10:01.304:D/dalvikvm（19206）：threadid=16:通知调试器
06-21 14:10:01.304:D/dalvikvm（19206）：threadid=16(RefQueueWorker@org.apache.http.impl.conn.tsccm.ConnPoolByRoute@427f7c80）：调用run（）
06-21 14:10:01.309:I/System.out（19206）：httpget:http://192.168.71.1/json/?app=0b52765ac1d697a37891605df3c27e0f
06-21 14:10:01.310:I/系统输出（19206）：http://192.168.71.1/json/?app=0b52765ac1d697a37891605df3c27e0f
06-21 14:10:01.310:D/dalvikvm（19206）：创建内部线程：堆栈大小=128KB
06-21 14:10:01.310:D/dalvikvm（19206）：创建新线程
06-21 14:10:01.310:D/dalvikvm（19206）：创建新线程
06-21 14:10:01.310:D/dalvikvm（19206）：更新线程列表
06-21 14:10:01.311:D/dalvikvm（19206）：threadid=17:0x616b9000处的内部堆栈
06-21 14:10:01.311:D/dalvikvm（19206）：threadid=17：从interp创建
06-21 14:10:01.311:D/dalvikvm（19206）：启动新线程
06-21 14:10:01.311:D/dalvikvm（19206）：threadid=17:通知调试器
06-21 14:10:01.311:D/dalvikvm（19206）：threadid=17（pool-1-thread-1）：调用run（）
06-21 14:10:01.317:I/System.out（19206）：[socket][0]连接/192.168.71.1:80；LocalPort=56751（10000）
06-21 14:10:01.317:I/System.out（19206）：[CDS]连接[/192.168.71.1:80]tm:10
06-21 14:10:01.317:D/Posix（19206）：[Posix_connect Debug]Process com.example.json:80
06-21 14:10:01.318:I/System.out（19206）：[socket][/192.168.71.101:56751]已连接
06-21 14:10:01.318:I/System.out（19206）：[CDS]接收超时：10000
06-21 14:10:01.319:I/System.out（19206）：[CDS]因此超时：0
06-21 14:10:01.320:D/ActivityThread（19206）：ACT-AM_ON__RESUME_称为ActivityRecord{41f53428 token=android.os。BinderProxy@41f52b48{com.example.json/com.example.json.MainActivity}
06-21 14:10:01.321:I/System.out（19206）：>doSendRequest
06-21 14:10:01.323:I/System.out（19206）：num\u buffers=4，surface->num\u frames=3，win\u min\u undequeued=1
06-21 14:10:01.378:I/MaliEGL（19206）：[马里]允许的最大缓冲区数=3
06-21 14:10:01.378:D/GraphicBuffer（19206）：关闭手柄（0x617e0348）（w:544 h:960 f:1）
06-21 14:10:01.380:I/（19206）：[custom_prop]custom_get_string->module[browser]，key[UAProfileURL]
06-21 14:10:01.380:I/（19206）：[自定义属性]重置解析器->保留[0]
06-21 14:10:01.380:I/（19206）：[自定义属性]输入状态值
06-21 14:10:01.380:I/（19206）：[自定义属性]重置解析器->保留[1]
06-21 14:10:01.380:D/GraphicBuffer（19206）：创建句柄（0x617e2de8）（w:544，h:960，f:1）
06-21 14:10:01.382:D/OpenGLRenderer（19206）：启用调试模式0
06-21 14:10:01.382:I/（19206）：[自定义属性]输入状态值
06-21 14:10:01.382:I/（19206）：[自定义属性]重置解析器->保留[1]
06-21 14:10:01.382:I/（19206）：[自定义属性]输入状态值
06-21 14:10:01.382:I/（19206）：[自定义属性]重置解析器->保留[1]
06-21 14:10:01.382:I/（19206）：[自定义属性]输入状态值
06-21 14:10:01.382:I/（19206）：[定制道具]进入状态道具
06-21 14:10:01.382:I/（19206）：[定制道具]道具名称：ro.build.version.release
06-21 14:10:01.382:I/（19206）：[自定义属性]输入状态值
06