通过研究和支持，我创建了一个通过JSON数据填充的项目列表。我希望当用户点击其中一个项目数组时，它会将它们重定向到另一个活动，以便为他们提供有关它的更多信息。在帮助下，我试图弄清楚代码，即使有了帮助，到目前为止我的尝试都没有成功。
特别是，我在代码的这一部分遇到以下错误：
listview.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(EventsActivity.this,EventSingleItemActivity.class);
intent.putExtra("id_item", id);//this is id of the item that you said it. for example id:5544323 from your JSON web service
intent.putExtra("position", position); //order position in listview 0-1-2-3...
startActivity(intent); //start Activity
}
}
我收到错误的地方有：
“ItemClickListener类型的onItemClick方法（AdapterView，View，int，long）必须覆盖或实现超类型方法”
“在范围内无法访问EventsActivity类型的封闭实例”
“无法从类型Activity”
中对非静态方法startActivity（Intent）进行静态引用完整的代码可以在下面找到
public class EventsActivity extends Activity{
private static final String URL_WEB_SERVICE = "http://dooba.ca/analytics/ed.php";
private GridView gv;
private ArrayList<Events_List> container;
private ArrayList<Events_List> items;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.events_list_layout);
gv = (GridView) findViewById(R.id.gridview);
container = new ArrayList<Events_List>();
//download JSON
listDownload();
//add interface ItemClickListener
public interface ItemClickListener {
listview.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(EventsActivity.this,EventSingleItemActivity.class);
intent.putExtra("id_item", id);//this is id of the item that you said it. for example id:5544323 from your JSON web service
intent.putExtra("position", position); //order position in listview 0-1-2-3...
startActivity(intent); //start Activity
}
}
//catch in the second activity values
long id_item = getIntent().getExtras().getLong("id_item");
int position = getIntent().getExtras().getInt("id_item");
//Adding reference to id of the item from your json we service in adapter
public long getItemId(int position) {
return items.get(position).id;
}
}}
public void listDownload(){
RequestQueue volley = Volley.newRequestQueue(this);
JsonObjectRequest json = new JsonObjectRequest(Method.GET, URL_WEB_SERVICE, null, ResponseListener(), ErrorListener());
volley.add(json);
}
private Response.Listener<JSONObject> ResponseListener() {
return new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
try {
//your JSON Array
JSONArray array = response.getJSONArray("list_item");
for(int i = 0; i < array.length(); i++){
container.add(convertirAnuncio(array.getJSONObject(i)));
}
} catch (JSONException e) {
e.printStackTrace();
}
gv.setAdapter(new AdapterEvents(getApplicationContext(),container));
}
};
};
private Response.ErrorListener ErrorListener() {
return new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) { }
};
}
//object JSON
private final Events_List convertirAnuncio(JSONObject obj) throws JSONException {
long id = obj.getLong("id"); //id
String list_item_name = obj.getString("list_item_name");
String list_item_description = obj.getString("list_item_description");
String list_item_price = obj.getString("list_item_price");
Uri uri = Uri.parse(obj.getString("list_item_bac"));
return new Events_List(id,list_item_name,list_item_description,list_item_price, uri);
}
}
提前致谢
根据收到的好建议进行更新
我已根据评论更新了代码，现在面临以下小问题： listview无法解析，在以下行中生成错误：
listview.setOnItemClickListener(new OnItemClickListener(){
我还遇到了一个次要的格式化问题，我试图通过右键单击＆gt;来解决这个问题。来源＆gt;格式，但错误仍然存在
listview.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(EventsActivity.this,EventSingleItemActivity.class);
intent.putExtra("id_item", id);//this is id of the item that you said it. for example id:5544323 from your JSON web service
intent.putExtra("position", position); //order position in listview 0-1-2-3...
startActivity(intent); //start Activity
}
}
完成下面的更新代码
public class EventsActivity extends Activity{
private static final String URL_WEB_SERVICE = "http://dooba.ca/analytics/ed.php";
private GridView gv;
private ArrayList<Events_List> container;
private ArrayList<Events_List> items;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.events_list_layout);
gv = (GridView) findViewById(R.id.gridview);
container = new ArrayList<Events_List>();
//download JSON
listDownload();
listview.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(EventsActivity.this,EventSingleItemActivity.class);
intent.putExtra("id_item", id);//this is id of the item that you said it. for example id:5544323 from your JSON web service
intent.putExtra("position", position); //order position in listview 0-1-2-3...
startActivity(intent); //start Activity
}
}
public void listDownload(){
RequestQueue volley = Volley.newRequestQueue(this);
JsonObjectRequest json = new JsonObjectRequest(Method.GET, URL_WEB_SERVICE, null, ResponseListener(), ErrorListener());
volley.add(json);
}
private Response.Listener<JSONObject> ResponseListener() {
return new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
try {
//your JSON Array
JSONArray array = response.getJSONArray("list_item");
for(int i = 0; i < array.length(); i++){
container.add(convertirAnuncio(array.getJSONObject(i)));
}
} catch (JSONException e) {
e.printStackTrace();
}
gv.setAdapter(new AdapterEvents(getApplicationContext(),container));
}
};
};
private Response.ErrorListener ErrorListener() {
return new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) { }
};
}
//object JSON
private final Events_List convertirAnuncio(JSONObject obj) throws JSONException {
long id = obj.getLong("id"); //id
String list_item_name = obj.getString("list_item_name");
String list_item_description = obj.getString("list_item_description");
String list_item_price = obj.getString("list_item_price");
Uri uri = Uri.parse(obj.getString("list_item_bac"));
return new Events_List(id,list_item_name,list_item_description,list_item_price, uri);
}
更新2 我从logcat收到了以下消息。我已经清理了我的项目，并且已经验证了清单中引用了活动。我相信这可能是以下代码的问题。
Logcat消息：
08-04 20:00:30.492: E/AndroidRuntime(1481): FATAL EXCEPTION: main
08-04 20:00:30.492: E/AndroidRuntime(1481): Process: com.dooba.beta, PID: 1481
08-04 20:00:30.492: E/AndroidRuntime(1481): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dooba.beta/com.dooba.beta.EventsActivity}: java.lang.NullPointerException
08-04 20:00:30.492: E/AndroidRuntime(1481): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
08-04 20:00:30.492: E/AndroidRuntime(1481): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
08-04 20:00:30.492: E/AndroidRuntime(1481): at android.app.ActivityThread.access$800(ActivityThread.java:135)
08-04 20:00:30.492: E/AndroidRuntime(1481): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
08-04 20:00:30.492: E/AndroidRuntime(1481): at android.os.Handler.dispatchMessage(Handler.java:102)
08-04 20:00:30.492: E/AndroidRuntime(1481): at android.os.Looper.loop(Looper.java:136)
08-04 20:00:30.492: E/AndroidRuntime(1481): at android.app.ActivityThread.main(ActivityThread.java:5017)
08-04 20:00:30.492: E/AndroidRuntime(1481): at java.lang.reflect.Method.invokeNative(Native Method)
08-04 20:00:30.492: E/AndroidRuntime(1481): at java.lang.reflect.Method.invoke(Method.java:515)
08-04 20:00:30.492: E/AndroidRuntime(1481): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
08-04 20:00:30.492: E/AndroidRuntime(1481): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
08-04 20:00:30.492: E/AndroidRuntime(1481): at dalvik.system.NativeStart.main(Native Method)
08-04 20:00:30.492: E/AndroidRuntime(1481): Caused by: java.lang.NullPointerException
08-04 20:00:30.492: E/AndroidRuntime(1481): at com.dooba.beta.EventsActivity.onCreate(EventsActivity.java:54)
08-04 20:00:30.492: E/AndroidRuntime(1481): at android.app.Activity.performCreate(Activity.java:5231)
08-04 20:00:30.492: E/AndroidRuntime(1481): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
08-04 20:00:30.492: E/AndroidRuntime(1481): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
08-04 20:00:30.492: E/AndroidRuntime(1481): ... 11 more
更新后的活动代码：
public class EventsActivity extends Activity{
private static final String URL_WEB_SERVICE = "http://dooba.ca/analytics/ed.php";
private GridView gv;
private ArrayList<Events_List> container;
private ArrayList<Events_List> items;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.events_list_layout);
gv = (GridView) findViewById(R.id.gridview);
container = new ArrayList<Events_List>();
//download JSON
listDownload();
ListView s = (ListView) findViewById(R.id.listViewSingleClick);
s.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(EventsActivity.this,EventSingleItemActivity.class);
intent.putExtra("id_item", id);//this is id of the item that you said it. for example id:5544323 from your JSON web service
intent.putExtra("position", position); //order position in listview 0-1-2-3...
startActivity(intent); //start Activity
}
});
}
public void listDownload(){
RequestQueue volley = Volley.newRequestQueue(this);
JsonObjectRequest json = new JsonObjectRequest(Method.GET, URL_WEB_SERVICE, null, ResponseListener(), ErrorListener());
volley.add(json);
}
private Response.Listener<JSONObject> ResponseListener() {
return new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
try {
//your JSON Array
JSONArray array = response.getJSONArray("list_item");
for(int i = 0; i < array.length(); i++){
container.add(convertirAnuncio(array.getJSONObject(i)));
}
} catch (JSONException e) {
e.printStackTrace();
}
gv.setAdapter(new AdapterEvents(getApplicationContext(),container));
}
};
};
private Response.ErrorListener ErrorListener() {
return new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) { }
};
}
//object JSON
private final Events_List convertirAnuncio(JSONObject obj) throws JSONException {
long id = obj.getLong("id"); //id
String list_item_name = obj.getString("list_item_name");
String list_item_description = obj.getString("list_item_description");
String list_item_price = obj.getString("list_item_price");
Uri uri = Uri.parse(obj.getString("list_item_bac"));
return new Events_List(id,list_item_name,list_item_description,list_item_price, uri);
}
}
答案 0 :(得分：1)
<强>问题：
public interface ItemClickListener {
您正在将方法调用包装到setOnItemClickListener，这完全在不同的范围内，从而为您提供这些错误，我不知道为什么要将接口放在onCreate方法中，这实际上是一个糟糕的设计。< / p>
<强>溶液
只需删除public interface ItemClickListener {即可使用该类的引用，而不是ItemClickListener。
修改
ListView s = (ListView) findViewById(R.id.id_to_list_view);
编辑2：
setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
}
});
答案 1 :(得分：1)
试试这段代码： 删除你的接口代码和getItem代码..这就是使itemClickListener工作所需的一切。
listview.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(EventsActivity.this,EventSingleItemActivity.class);
intent.putExtra("id_item", id);//this is id of the item that you said it. for example id:5544323 from your JSON web service
intent.putExtra("position", position); //order position in listview 0-1-2-3...
startActivity(intent); //start Activity
}
}