我发布了“id”值（我通过getintent传递给了这个活动）
Uid = getIntent().getStringExtra("id");
到服务器并检索相应的jsonobjects。
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<String, String>();
params.put("id", Uid);
return params;
}
当我的jsonarray为空时，我的应用程序崩溃了。我想在jsonarray为空时敬酒“错误”。我怎样才能解决这个问题？
这是我的代码：
public class kill extends FragmentActivity {
GridView grid1;
CustomGrid_Album adapter;
private ProgressDialog pDialog;
String Uid,Disp;
public String category;
public String selected;
public static String imagename;
Button Alb_sel;
ArrayList<Item_album> gridArray = new ArrayList<Item_album>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.album_display);
grid1 = (GridView) findViewById(R.id.gridView2);
Uid = getIntent().getStringExtra("id");
Disp = getIntent().getStringExtra("disp");
Alb_sel=(Button)findViewById(R.id.album_to_select);
pDialog = new ProgressDialog(kill.this);
pDialog.setMessage("Loading...");
pDialog.show();
//fetching JSONArray
final RequestQueue queue = Volley.newRequestQueue(getApplicationContext());
StringRequest stringRequest = new StringRequest(com.android.volley.Request.Method.POST, AppConfig.URL_Gallery4,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Datas.imageIds = new String[response.length()];
JSONArray arr = null;
try {
arr = new JSONArray(response);
} catch (JSONException e1) {
e1.printStackTrace();
}
int i=0;
for (i = 0; i < arr.length(); i++) {
try {
JSONObject obj = arr.getJSONObject(i);
category = obj.getString("category_name");
selected = obj.getString("album_id");
imagename = obj.getString("org_image_name");
Datas.imageIds[i] = AppConfig.URL_IMAGE_temp+obj.getString("album_image").substring(3);
gridArray.add(new Item_album(Datas.imageIds[i]));
} catch (JSONException e) {
e.printStackTrace();
}
}
final int xl = i;
adapter = new CustomGrid_Album(kill.this,xl,gridArray);
adapter.notifyDataSetChanged();
grid1.setAdapter(adapter);
pDialog.dismiss();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getApplicationContext(), "No images in this gallery", Toast.LENGTH_SHORT).show();
error.printStackTrace();
}
})
{
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<String, String>();
params.put("id", Uid);
return params;
}
};
queue.add(stringRequest);
}
}
答案 0 :(得分：1)
在 onResponse
中应用支票if(response.length()==0){
// error message
}else{
// your rest of the code
}
答案 1 :(得分：1)
这看起来有问题。
Datas.imageIds = new String[response.length()];
您不希望数组具有字符串的大小。您需要响应中的JSONArray 大小的数组。
public void onResponse(String response) {
JSONArray arr = null;
try {
arr = new JSONArray(response);
Datas.imageIds = new String[arr.length()];
} catch (JSONException e1) {
e1.printStackTrace();
}
但是，如果在那里抛出异常，你的代码将继续运行，那么你最终会得到一个NullPointerException，因此你也应该将for循环移动到try-catch。
但实际上，如果你期望JSONArrayRequest，你应该使用JSONArray。
我想在jsonarray为空时敬酒“错误”
足够简单。
arr = new JSONArray(response);
if (arr.length() == 0) {
// TODO: Toast
}
答案 2 :(得分：0)
我只需在onResponse方法中添加两项检查：
...
public void onResponse(String response) {
// Check if the response itself is an empty string or null
if(TextUtils.isEmpty(response)) {
// Show your user feedback
return;
}
Datas.imageIds = new String[response.length()];
JSONArray arr = null;
try {
arr = new JSONArray(response);
// Check if your JSON has no elements in it
if(arr.length == 0) {
// Show your user feedback
return;
}
} catch (JSONException e1) {
e1.printStackTrace();
}
...
答案 3 :(得分：0)
您已声明JSONArray arr = null;
之后，将服务器的JSON分配给该JSONArray。
获得
后添加一行if(arr==null)
{
//toast
}
else
{
//whatever you want to do with JSON
}
答案 4 :(得分：0)
StringRequest stringRequest = new StringRequest(com.android.volley.Request.Method.POST, AppConfig.URL_Gallery4,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
if(response.length()==0){
Toast.makeText(getActivity(),"no data found",Toast.LENGTH_SHORT).show();
}
else{
Datas.imageIds = new String[response.length()];
JSONArray arr = null;
try {
arr = new JSONArray(response);
} catch (JSONException e1) {
e1.printStackTrace();
}
if(arr.length()>0){
int i=0;
for (i = 0; i < arr.length(); i++) {
try {
JSONObject obj = arr.getJSONObject(i);
category = obj.getString("category_name");
selected = obj.getString("album_id");
imagename = obj.getString("org_image_name");
Datas.imageIds[i] = AppConfig.URL_IMAGE_temp+obj.getString("album_image").substring(3);
gridArray.add(new Item_album(Datas.imageIds[i]));
} catch (JSONException e) {
e.printStackTrace();
}
}
final int xl = i;
adapter = new CustomGrid_Album(kill.this,xl,gridArray);
adapter.notifyDataSetChanged();
grid1.setAdapter(adapter);
}else{
Toast.makeText(getActivity(),"no data found",Toast.LENGTH_SHORT).show();
}
}
pDialog.dismiss();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getApplicationContext(), "No images in this gallery", Toast.LENGTH_SHORT).show();
error.printStackTrace();
}
})
{
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<String, String>();
params.put("id", Uid);
return params;
}
};
答案 5 :(得分：0)
使用以下代码检查响应是否为null，并在对象中检查它是否具有键或具有键的数据不为空
if(response!=null){
try {
Datas.imageIds = new String[response.length()];
JSONArray arr = new JSONArray(response);
for (int i = 0; i < arr.length(); i++) {
try {
JSONObject obj = arr.getJSONObject(i);
if(obj!=null){
if(obj.has("category_name") && !obj.isNull("category_name"){
category = obj.getString("category_name");
}
if(obj.has("album_id") && !obj.isNull("album_id"){
selected = obj.getString("album_id");
}
if(obj.has("org_image_name") && !obj.isNull("org_image_name"){
imagename = obj.getString("org_image_name");
}
if(obj.has("album_image") && !obj.isNull("album_image"){
Datas.imageIds[i] = AppConfig.URL_IMAGE_temp+obj.getString("album_image").substring(3);
gridArray.add(new Item_album(Datas.imageIds[i]));
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
final int xl = i;
adapter = new CustomGrid_Album(kill.this,xl,gridArray);
adapter.notifyDataSetChanged();
grid1.setAdapter(adapter);
pDialog.dismiss();
} catch (JSONException e1) {
e1.printStackTrace();
}
}
答案 6 :(得分：0)
您正在使用StringRequest，而不是使用JsonArrayRequest来发出请求，如下所示，当响应中存在有效的JSONArray时，您将在onResponse方法中获得响应，如果没有数据，那么您将在onError方法中获得响应
JsonArrayRequest rReq = new JsonArrayRequest（Request.Method.GET，＆＃34; url＆＃34;，new JSONObject（），new Response.Listener（）{ @覆盖 public void onResponse（JSONArray response）{ Log.e（TAG，＆＃34; onResponse：＆＃34; + response.toString（））;
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.e(TAG, "onErrorResponse: "+error.getMessage() );
}
})