我试图从我的第一个片段中的url获取信息，但似乎我的第一个片段给了我2个错误
第一次出现错误
adapter = new ListViewAdapter(FirstFragment.this, arraylist);
，第二次
public class FirstFragment extends Fragment {
View myView;
@Nullable
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
myView = inflater.inflate(R.layout.first_layout, container ,false);
new DownloadJSON().execute();
return myView;
}
JSONObject jsonobject;
JSONArray jsonarray;
ListView listview;
ListViewAdapter adapter;
ProgressDialog mProgressDialog;
ArrayList<HashMap<String, String>> arraylist;
static String RANK = "rank";
static String COUNTRY = "country";
static String POPULATION = "population";
static String FLAG = "flag";
// DownloadJSON AsyncTask
private class DownloadJSON extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(FirstFragment.this);
// Set progressdialog title
mProgressDialog.setTitle("Actualizando Información");
// Set progressdialog message
mProgressDialog.setMessage("Cargando...");
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected Void doInBackground(Void... params) {
// Create an array
arraylist = new ArrayList<HashMap<String, String>>();
// Retrieve JSON Objects from the given URL address
jsonobject = JSONfunctions
.getJSONfromURL("http://www.androidbegin.com/tutorial/jsonparsetutorial.txt");
try {
// Locate the array name in JSON
jsonarray = jsonobject.getJSONArray("worldpopulation");
for (int i = 0; i < jsonarray.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
// Retrive JSON Objects
map.put("rank", jsonobject.getString("rank"));
map.put("country", jsonobject.getString("country"));
map.put("population", jsonobject.getString("population"));
map.put("flag", jsonobject.getString("flag"));
// Set the JSON Objects into the array
arraylist.add(map);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void args) {
// Locate the listview in listview_main.xml
listview = (ListView) myView.findViewById(R.id.listview);
// Pass the results into ListViewAdapter.java
adapter = new ListViewAdapter(FirstFragment.this, arraylist);
// Set the adapter to the ListView
listview.setAdapter(adapter);
// Close the progressdialog
mProgressDialog.dismiss();
}
}
}
这是我的FirstFragment类
public class ListViewAdapter extends BaseAdapter {
// Declare Variables
Context context;
LayoutInflater inflater;
ArrayList<HashMap<String, String>> data;
ImageLoader imageLoader;
HashMap<String, String> resultp = new HashMap<String, String>();
public ListViewAdapter(Context context,
ArrayList<HashMap<String, String>> arraylist) {
this.context = context;
data = arraylist;
imageLoader = new ImageLoader(context);
}
@Override
public int getCount() {
return data.size();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
public View getView(final int position, View convertView, ViewGroup parent) {
// Declare Variables
TextView rank;
TextView country;
TextView population;
ImageView flag;
inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View itemView = inflater.inflate(R.layout.listview_item, parent, false);
// Get the position
resultp = data.get(position);
// Locate the TextViews in listview_item.xml
rank = (TextView) itemView.findViewById(R.id.rank);
country = (TextView) itemView.findViewById(R.id.country);
population = (TextView) itemView.findViewById(R.id.population);
// Locate the ImageView in listview_item.xml
flag = (ImageView) itemView.findViewById(R.id.flag);
// Capture position and set results to the TextViews
rank.setText(resultp.get(FirstFragment.RANK));
country.setText(resultp.get(FirstFragment.COUNTRY));
population.setText(resultp.get(FirstFragment.POPULATION));
// Capture position and set results to the ImageView
// Passes flag images URL into ImageLoader.class
imageLoader.DisplayImage(resultp.get(FirstFragment.FLAG), flag);
// Capture ListView item click
itemView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// Get the position
resultp = data.get(position);
Intent intent = new Intent(context, SingleItemView.class);
// Pass all data rank
intent.putExtra("rank", resultp.get(FirstFragment.RANK));
// Pass all data country
intent.putExtra("country", resultp.get(FirstFragment.COUNTRY));
// Pass all data population
intent.putExtra("population",resultp.get(FirstFragment.POPULATION));
// Pass all data flag
intent.putExtra("flag", resultp.get(FirstFragment.FLAG));
// Start SingleItemView Class
context.startActivity(intent);
}
});
return itemView;
}
}
这是我的listviewadapter类
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
@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();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.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);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
android.app.FragmentManager fragmentManager = getFragmentManager();
if (id == R.id.nav_first_layout) {
fragmentManager.beginTransaction().replace(R.id.content_frame,new FirstFragment()).commit();
// Handle the camera action
} else if (id == R.id.nav_second_layout) {
fragmentManager.beginTransaction().replace(R.id.content_frame,new SecondFragment()).commit();
} else if (id == R.id.nav_third_layout) {
fragmentManager.beginTransaction().replace(R.id.content_frame,new ThirdFragment()).commit();
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
这是我的主要活动课程，如果需要
Error:(58, 31) error: no suitable constructor found for ProgressDialog(FirstFragment)
constructor ProgressDialog.ProgressDialog(Context,int) is not applicable
(actual and formal argument lists differ in length)
constructor ProgressDialog.ProgressDialog(Context) is not applicable
(actual argument FirstFragment cannot be converted to Context by method invocation conversion)
Error:(107, 23) error: constructor ListViewAdapter in class ListViewAdapter cannot be applied to given types;
required: Context,ArrayList<HashMap<String,String>>
found: FirstFragment,ArrayList<HashMap<String,String>>
reason: actual argument FirstFragment cannot be converted to Context by method invocation conversion
logcat的
def initial(request):
return render(request,'display/home.html')
def upload(request):
f = FileForm()
f=FileModel.objects.all()
print(f)
y="Hello"
if request.method== 'POST':
fil=FileForm(request.POST,request.FILES)
if fil.is_valid():
newfile=FileModel(file=request.FILES['file'])
newfile.save()
return HttpResponseRedirect(reverse('display.views.list'))
else:
fil=FileForm()
docs=FileModel.objects.all()
return render(request,"display/upload.html",{"y":y})
由于
答案 0 :(得分：0)
两次你都试图将片段传递给这些类的构造函数。片段不是活动，因此当构造函数需要用于实例化的上下文时，您不能仅传递片段。相反，请使用getActivity()方法。此方法返回与片段关联的活动。所以：
mProgressDialog = new ProgressDialog(getActivity());
和
adapter = new ListViewAdapter(getActivity(), arraylist);
进一步阅读：https://developer.android.com/reference/android/app/Fragment.html