我是android和stackoverflow的新手。
我有一个带有2个按钮和1个textview的android工作室项目，用于解析带有齐射的json（对象和数组）。
我的应用程序编译没有任何错误并运行。但当我点击我的一个按钮（对于解析对象和数组）时，我的应用程序就会关闭！ 我的MainActivity，myVolleyController和清单文件：
package net.aminapps.volleyjson;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.JsonObjectRequest;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
private static final String URLJsonObject="http://api.androidhive.info/volley/person_object.json";
private static final String URLJsonArry = "http://api.androidhive.info/volley/person_array.json";
private static String TAG = MainActivity.class.getSimpleName();
public Button btnMakeObjectRequest,btnMakeArrayRequest;
private ProgressDialog pDialog;
private TextView txtResponse;
private String jsonResponse;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
btnMakeObjectRequest = (Button) findViewById(R.id.btnObjRequest);
btnMakeArrayRequest = (Button) findViewById(R.id.btnArrayRequest);
txtResponse = (TextView) findViewById(R.id.txtResponse);
pDialog = new ProgressDialog(this);
pDialog.setMessage("Please wait...");
pDialog.setCancelable(false);
btnMakeObjectRequest.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
makeJsonObjectRequest();
}
});
btnMakeArrayRequest.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
makeJsonArrayRequest();
}
});
}
private void makeJsonObjectRequest() {
showpDialog();
JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET,
URLJsonObject, null, new Response.Listener<JSONObject>() {
public void onResponse(JSONObject response) {
Log.d(TAG, response.toString());
try {
String name = response.getString("name");
String email = response.getString("email");
JSONObject phone = response.getJSONObject("phone");
String home = phone.getString("home");
String mobile = phone.getString("mobile");
jsonResponse = "";
jsonResponse += "Name: " + name + "\n\n";
jsonResponse += "Email: " + email + "\n\n";
jsonResponse += "Home: " + home + "\n\n";
jsonResponse += "Mobile: " + mobile + "\n\n";
txtResponse.setText(jsonResponse);
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getApplicationContext(),
"Error: " + e.getMessage(),
Toast.LENGTH_LONG).show();
}
hidepDialog();
}
}, new Response.ErrorListener() {
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
Toast.makeText(getApplicationContext(),
error.getMessage(), Toast.LENGTH_SHORT).show();
// hide the progress dialog
hidepDialog();
}
});
myVolleyController.getInstance().addToRequestQueue(jsonObjReq);
}
private void makeJsonArrayRequest() {
showpDialog();
JsonArrayRequest req = new JsonArrayRequest(URLJsonArry,
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
Log.d(TAG, response.toString());
try {
jsonResponse = "";
for (int i = 0; i < response.length(); i++) {
JSONObject person = (JSONObject) response.get(i);
String name = person.getString("name");
String email = person.getString("email");
JSONObject phone = person
.getJSONObject("phone");
String home = phone.getString("home");
String mobile = phone.getString("mobile");
jsonResponse += "Name: " + name + "\n\n";
jsonResponse += "Email: " + email + "\n\n";
jsonResponse += "Home: " + home + "\n\n";
jsonResponse += "Mobile: " + mobile + "\n\n\n";
}
txtResponse.setText(jsonResponse);
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getApplicationContext(),
"Error: " + e.getMessage(),
Toast.LENGTH_LONG).show();
}
hidepDialog();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
Toast.makeText(getApplicationContext(),
error.getMessage(), Toast.LENGTH_SHORT).show();
hidepDialog();
}
});
myVolleyController.getInstance().addToRequestQueue(req);
}
private void showpDialog() {
if (!pDialog.isShowing())
pDialog.show();
}
private void hidepDialog() {
if (pDialog.isShowing())
pDialog.dismiss();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
package net.aminapps.volleyjson;
import android.app.Application;
import android.app.DownloadManager;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.Volley;
/**
* Created by My PC on 12/14/2016.
*/
public class myVolleyController extends Application {
public static final String TAG = myVolleyController.class.getSimpleName();
private RequestQueue myRQ;
private static myVolleyController myInstance;
public void onCreate() {
super.onCreate();
myInstance = this;
}
public static synchronized myVolleyController getInstance() {
return myInstance;
}
public RequestQueue getRequestQueue() {
if (myRQ == null) {
myRQ = Volley.newRequestQueue(getApplicationContext());
}
return myRQ;
}
public <T> void addToRequestQueue(Request<T> req, String tag) {
req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
getRequestQueue().add(req);
}
public <T> void addToRequestQueue(Request<T> req) {
req.setTag(TAG);
getRequestQueue().add(req);
}
public void cancelPendingRequests(Object tag) {
if (myRQ != null) {
myRQ.cancelAll(tag);
}
}
}
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="net.aminapps.volleyjson">
<uses-permission android:name="android.permission.INTERNET"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme"
>
<activity
android:name=".MainActivity"
android:label="@string/app_name"
android:theme="@style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
这是我的logcat（我检查但无法理解问题出在哪里！）：
12-19 01:26:16.111 31003-31003/net.aminapps.volleyjson I/InjectionManager: Inside getClassLibPath + mLibMap{0=, 1=}
12-19 01:26:16.121 31003-31003/net.aminapps.volleyjson I/InjectionManager: Inside getClassLibPath caller
12-19 01:26:16.161 31003-31003/net.aminapps.volleyjson D/InjectionManager: InjectionManager
12-19 01:26:16.161 31003-31003/net.aminapps.volleyjson D/InjectionManager: fillFeatureStoreMap net.aminapps.volleyjson
12-19 01:26:16.161 31003-31003/net.aminapps.volleyjson I/InjectionManager: Constructor net.aminapps.volleyjson, Feature store :{}
12-19 01:26:16.161 31003-31003/net.aminapps.volleyjson I/InjectionManager: featureStore :{}
12-19 01:26:16.241 31003-31003/net.aminapps.volleyjson D/SecWifiDisplayUtil: Metadata value : SecSettings2
12-19 01:26:16.271 31003-31003/net.aminapps.volleyjson W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
12-19 01:26:16.311 31003-31003/net.aminapps.volleyjson D/PhoneWindow: *FMB* installDecor mIsFloating : false
12-19 01:26:16.311 31003-31003/net.aminapps.volleyjson D/PhoneWindow: *FMB* installDecor flags : -2139029248
12-19 01:26:16.391 31003-31003/net.aminapps.volleyjson D/Activity: performCreate Call Injection manager
12-19 01:26:16.391 31003-31003/net.aminapps.volleyjson I/InjectionManager: dispatchOnViewCreated > Target : net.aminapps.volleyjson.MainActivity isFragment :false
12-19 01:26:16.391 31003-31037/net.aminapps.volleyjson D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true
12-19 01:26:16.411 31003-31003/net.aminapps.volleyjson D/PhoneWindow: *FMB* isFloatingMenuEnabled mFloatingMenuBtn : null
12-19 01:26:16.411 31003-31003/net.aminapps.volleyjson D/PhoneWindow: *FMB* isFloatingMenuEnabled return false
12-19 01:26:16.461 31003-31003/net.aminapps.volleyjson D/SRIB_DCS: log_dcs ThreadedRenderer::initialize entered!
12-19 01:26:16.501 31003-31037/net.aminapps.volleyjson D/libEGL: loaded /vendor/lib64/egl/libGLES_mali.so
12-19 01:26:16.531 31003-31037/net.aminapps.volleyjson D/libEGL: eglInitialize EGLDisplay = 0x7f85ba08b8
12-19 01:26:16.531 31003-31037/net.aminapps.volleyjson I/OpenGLRenderer: Initialized EGL, version 1.4
12-19 01:26:16.551 31003-31037/net.aminapps.volleyjson I/OpenGLRenderer: HWUI protection enabled for context , &this =0x7f9401b940 ,&mEglDisplay = 1 , &mEglConfig = -1810767184
12-19 01:26:16.551 31003-31037/net.aminapps.volleyjson D/OpenGLRenderer: Get maximum texture size. GL_MAX_TEXTURE_SIZE is 8192
12-19 01:26:16.551 31003-31037/net.aminapps.volleyjson D/OpenGLRenderer: Enabling debug mode 0
12-19 01:26:16.551 31003-31037/net.aminapps.volleyjson D/mali_winsys: new_window_surface returns 0x3000, [1440x2560]-format:1
12-19 01:26:16.571 31003-31003/net.aminapps.volleyjson V/ActivityThread: updateVisibility : ActivityRecord{b3f715 token=android.os.BinderProxy@6df2a88 {net.aminapps.volleyjson/net.aminapps.volleyjson.MainActivity}} show : true
12-19 01:26:16.771 31003-31003/net.aminapps.volleyjson I/InjectionManager: dispatchCreateOptionsMenu :net.aminapps.volleyjson.MainActivity
12-19 01:26:16.771 31003-31003/net.aminapps.volleyjson I/InjectionManager: dispatchPrepareOptionsMenu :net.aminapps.volleyjson.MainActivity
12-19 01:26:16.811 31003-31003/net.aminapps.volleyjson W/IInputConnectionWrapper: showStatusIcon on inactive InputConnection
12-19 01:26:16.811 31003-31003/net.aminapps.volleyjson I/Timeline: Timeline: Activity_idle id: android.os.BinderProxy@6df2a88 time:338081977
12-19 01:26:37.901 31003-31003/net.aminapps.volleyjson I/Timeline: Timeline: Activity_idle id: android.os.BinderProxy@6df2a88 time:338103064
12-19 01:26:38.631 31003-31003/net.aminapps.volleyjson D/ViewRootImpl: ViewPostImeInputStage ACTION_DOWN
12-19 01:26:39.151 31003-31003/net.aminapps.volleyjson V/ActivityThread: updateVisibility : ActivityRecord{b3f715 token=android.os.BinderProxy@6df2a88 {net.aminapps.volleyjson/net.aminapps.volleyjson.MainActivity}} show : false
12-19 01:26:41.751 31003-31003/net.aminapps.volleyjson D/SRIB_DCS: log_dcs ThreadedRenderer::initialize entered!
12-19 01:26:41.751 31003-31037/net.aminapps.volleyjson D/mali_winsys: new_window_surface returns 0x3000, [1440x2560]-format:1
12-19 01:26:41.791 31003-31003/net.aminapps.volleyjson I/Timeline: Timeline: Activity_idle id: android.os.BinderProxy@6df2a88 time:338106951
12-19 01:26:43.461 31003-31003/net.aminapps.volleyjson D/ViewRootImpl: ViewPostImeInputStage ACTION_DOWN
12-19 01:26:45.231 31003-31003/net.aminapps.volleyjson D/ViewRootImpl: ViewPostImeInputStage ACTION_DOWN
12-19 01:26:45.341 31003-31003/net.aminapps.volleyjson D/PhoneWindow: *FMB* installDecor mIsFloating : true
12-19 01:26:45.341 31003-31003/net.aminapps.volleyjson D/PhoneWindow: *FMB* installDecor flags : 8388610
12-19 01:26:45.371 31003-31017/net.aminapps.volleyjson I/art: Background sticky concurrent mark sweep GC freed 13230(2MB) AllocSpace objects, 3(60KB) LOS objects, 41% free, 3MB/5MB, paused 6.406ms total 28.855ms
12-19 01:26:45.391 31003-31003/net.aminapps.volleyjson D/AndroidRuntime: Shutting down VM
12-19 01:26:45.391 31003-31003/net.aminapps.volleyjson E/AndroidRuntime: FATAL EXCEPTION: main
Process: net.aminapps.volleyjson, PID: 31003
java.lang.NullPointerException: Attempt to invoke virtual method 'void net.aminapps.volleyjson.myVolleyController.addToRequestQueue(com.android.volley.Request)' on a null object reference
at net.aminapps.volleyjson.MainActivity.makeJsonObjectRequest(MainActivity.java:112)
at net.aminapps.volleyjson.MainActivity.access$000(MainActivity.java:30)
at net.aminapps.volleyjson.MainActivity$2.onClick(MainActivity.java:65)
at android.view.View.performClick(View.java:5254)
at android.widget.TextView.performClick(TextView.java:10557)
at android.view.View$PerformClick.run(View.java:21203)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6897)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
12-19 01:26:48.161 31003-31003/net.aminapps.volleyjson I/Process: Sending signal. PID: 31003 SIG: 9
答案 0 :(得分：1)
如果你正在使用单身myVolleyController，那么你可能还没有被添加到清单文件中。
<application
android:name="*your package*.myVolleyController">
.
.
.
.
</application>
答案 1 :(得分：0)
您可以在logcat中找到错误。可以在Android选项卡下的屏幕底部找到logcat。
修改 我相信你的问题在这里： 。myVolleyController.getInstance（）addToRequestQueue（REQ）;
getInstance（）方法似乎返回null，你永远不会创建你的对象。
编辑2：
public static synchronized myVolleyController getInstance() {
if(myInstance == null){
myInstance = new myVolleyController();
}
return myInstance;
}