我想通过单击listView中的项目来打开一个新活动。不幸的是我总是收到这个错误。尝试了几个教程并阅读了几个问题，我无法解决这个问题。
MainActivity.java
public class MainActivity extends Activity {
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle presses on the action bar items
switch (item.getItemId()) {
case R.id.action_email:
openMail();
return true;
case R.id.action_refresh:
refreshFeed();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public void openMail(){
Intent intent = new Intent(Intent.ACTION_SEND);
intent.setType("plain/text");
intent.putExtra(Intent.EXTRA_EMAIL, new String[] { "arjun@techulus.com" });
intent.putExtra(Intent.EXTRA_SUBJECT, "WFW");
//intent.putExtra(Intent.EXTRA_TEXT, "mail body");
startActivity(Intent.createChooser(intent, ""));
}
public void refreshFeed() {
listView = (ListView) findViewById(R.id.list);
feedItems = new ArrayList<FeedItem>();
listAdapter = new FeedListAdapter(this, feedItems);
listView.setAdapter(listAdapter);
listView.setOnItemClickListener(new ListView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> a, View v, int i, long l) {
openMail();
}
});
// making fresh volley request and getting json
JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
URL_FEED, null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
VolleyLog.d(TAG, "Response: " + response.toString());
if (response != null) {
parseJsonFeed(response);
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
}
}
);
// Adding request to volley request queue
AppController.getInstance().addToRequestQueue(jsonReq);
}
private static final String TAG = MainActivity.class.getSimpleName();
private ListView listView;
private FeedListAdapter listAdapter;
private List<FeedItem> feedItems;
private String URL_FEED = "http://wirefreeworld.in/api/list.php";
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ListView lv = getListView();
// listening to single list item on click
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// selected item
String product = "Test";
// Launching new Activity on selecting single List Item
Intent i = new Intent(getApplicationContext(), product.class);
// sending data to new activity
i.putExtra("product", product);
startActivity(i);
}
});
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.list);
feedItems = new ArrayList<FeedItem>();
listAdapter = new FeedListAdapter(this, feedItems);
listView.setAdapter(listAdapter);
// These two lines not needed,
// just to get the look of facebook (changing background color & hiding the icon)
getActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#333333")));
getActionBar().setIcon(
new ColorDrawable(getResources().getColor(android.R.color.transparent)));
// making fresh volley request and getting json
JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
URL_FEED, null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
VolleyLog.d(TAG, "Response: " + response.toString());
if (response != null) {
parseJsonFeed(response);
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
}
}
);
// Adding request to volley request queue
AppController.getInstance().addToRequestQueue(jsonReq);
}
/**
* Parsing json reponse and passing the data to feed view list adapter
* */
private void parseJsonFeed(JSONObject response) {
try {
JSONArray feedArray = response.getJSONArray("feed");
for (int i = 0; i < feedArray.length(); i++) {
JSONObject feedObj = (JSONObject) feedArray.get(i);
FeedItem item = new FeedItem();
item.setId(feedObj.getInt("id"));
item.setName(feedObj.getString("title"));
// Image might be null sometimes
String image = feedObj.isNull("photo1") ? null : feedObj
.getString("photo1");
item.setImge(image);
//item.setStatus(feedObj.getString("status"));
//item.setProfilePic("http://wirefreeworld.in/logo/logo.png");
//item.setTimeStamp(feedObj.getString("timeStamp"));
// url might be null sometimes
String feedUrl = feedObj.isNull("url") ? null : feedObj
.getString("url");
item.setUrl(feedUrl);
feedItems.add(item);
}
// notify data changes to list adapater
listAdapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
product.java
public class product extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_product);
TextView txtProduct = (TextView) findViewById(R.id.product_label);
Intent i = getIntent();
// getting attached intent data
String product = i.getStringExtra("product");
// displaying selected product name
txtProduct.setText(product);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.product, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
答案 0 :(得分：2)
为了让方法getListView()可用，您的活动类必须扩展ListActivity类，而不是Activity。
ListActivity具有默认布局，该布局由屏幕中央的单个全屏列表组成。但是，如果需要，可以通过在onCreate（）中使用setContentView（）设置自己的视图布局来自定义屏幕布局。要做到这一点，你自己的视图必须包含一个带有id＆＃34; @android：id / list＆＃34;的ListView对象。 （或列出代码中的代码）
答案 1 :(得分：0)
对于方法getListView()，您的活动类必须扩展ListActivity，并且您的布局必须包含标识为ListView的{{1}}对象
快乐编码：）