问题
I'm trying to call a method from one UI view that exists in a different class. These are two samples combined from the Android Developer site. I'll focus on one view for this question since the others are basically the same thing.
In my MainActivity.java, I'm setting up the Drawer navigation, populating the list, etc. I have a total of three fragments, each with their own XML for the UI, and each having their own Java class (extension of a Fragment) to handle their respective onCreateView. For one of these fragments, I have a button that calls the method getAddress. This method exists a separate class, LocationActivity.java, because the example code from the Android dev website requires it be an extension of Activity (plus a lot of these methods will be reused from the other fragments).
For my references to where_am_i_longlat.xml, this file just has the UI components. Sorry ran out of room for this post. There is a button in that XML that calls the getAddress button.
In the below code blocks, my where_am_i_longlat.xml has a button that calls the getAddress method. The getAddress method exists in LocationActivity.java. But it can't find that method, I'm guessing because its looking for it inside WhereAmILongLat.java? Plus, th method updates a textbox inside of where_am_i_longlat.xml. Any thoughts on how to go about this.
(Sorry if this is tagged incorrectly, I don't see one specifically for Android development)
MainActivity.java (builds the drawer and app navigation)
public class MainActivity extends FragmentActivity {
private String[] data;
private DrawerLayout drawer;
private ListView navList;
private ActionBarDrawerToggle mDrawerToggle;
private CharSequence mDrawerTitle;
private CharSequence mTitle;
final String[] fragments = {
"com.example.android.navigationdrawerexample.Home",
"com.example.android.navigationdrawerexample.WhereAmILongLat",
"com.example.android.navigationdrawerexample.WhereAmIAddress",
"com.example.android.navigationdrawerexample.WhatAmIDoing"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTitle = mDrawerTitle = getTitle();
data = getResources().getStringArray(R.array.navigation_array);
drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
navList = (ListView) findViewById(R.id.left_drawer);
drawer.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
navList.setAdapter(new ArrayAdapter<String>(getActionBar().getThemedContext(), R.layout.drawer_list_item, data));
navList.setOnItemClickListener(new DrawerItemClickListener());
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
// ActionBarDrawerToggle ties together the the proper interactions
// between the sliding drawer and the action bar app icon
mDrawerToggle = new ActionBarDrawerToggle(
this, /* host Activity */
drawer, /* DrawerLayout object */
R.drawable.ic_drawer, /* nav drawer image to replace 'Up' caret */
R.string.drawer_open, /* "open drawer" description for accessibility */
R.string.drawer_close /* "close drawer" description for accessibility */
) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(mTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(mDrawerTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
};
drawer.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
selectItem(0);
}
}
private class DrawerItemClickListener implements ListView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
}
private void selectItem(int pos) {
FragmentTransaction tx = getSupportFragmentManager().beginTransaction();
tx.replace(R.id.content_frame, Fragment.instantiate(MainActivity.this, fragments[pos]));
tx.commit();
navList.setItemChecked(pos, true);
setTitle(data[pos]);
drawer.closeDrawer(navList);
}
@Override
public void setTitle(CharSequence title) {
mTitle = title;
getActionBar().setTitle(mTitle);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
/* Called whenever we call invalidateOptionsMenu() */
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the nav drawer is open, hide action items related to the content view
boolean drawerOpen = drawer.isDrawerOpen(navList);
menu.findItem(R.id.action_websearch).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mDrawerToggle.syncState();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Pass any configuration change to the drawer toggls
mDrawerToggle.onConfigurationChanged(newConfig);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// The action bar home/up action should open or close the drawer.
// ActionBarDrawerToggle will take care of this.
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
// Handle action buttons
switch (item.getItemId()) {
case R.id.action_websearch:
// create intent to perform web search for this planet
Intent intent = new Intent(Intent.ACTION_WEB_SEARCH);
intent.putExtra(SearchManager.QUERY, getActionBar().getTitle());
// catch event that there's no activity to handle intent
if (intent.resolveActivity(getPackageManager()) != null) {
startActivity(intent);
} else {
Toast.makeText(this, R.string.app_not_available, Toast.LENGTH_LONG).show();
}
return true;
default:
return super.onOptionsItemSelected(item);
}
}
}
WhereAmILongLat.java (builds the UI specific from where_am_i_longlat.xml)
package com.example.android.navigationdrawerexample;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class WhereAmILongLat extends Fragment {
public static Fragment newInstance(Context context) {
WhereAmILongLat f = new WhereAmILongLat();
return f;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
ViewGroup root = (ViewGroup) inflater.inflate(R.layout.where_am_i_longlat, null);
return root;
}
}
LocationActivity.java. Where all of the Location based methods are.
public class LocationActivity extends FragmentActivity implements
LocationListener,
GooglePlayServicesClient.ConnectionCallbacks,
GooglePlayServicesClient.OnConnectionFailedListener {
// A request to connect to Location Services
private LocationRequest mLocationRequest;
// Stores the current instantiation of the location client in this object
private LocationClient mLocationClient;
// Handles to UI widgets
private TextView mLatLng;
private TextView mAddress;
private ProgressBar mActivityIndicator;
private TextView mConnectionState;
private TextView mConnectionStatus;
// Handle to SharedPreferences for this app
SharedPreferences mPrefs;
// Handle to a SharedPreferences editor
SharedPreferences.Editor mEditor;
boolean mUpdatesRequested = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Get handles to the UI view objects
mLatLng = (TextView) findViewById(R.id.lat_lng);
mAddress = (TextView) findViewById(R.id.address);
mActivityIndicator = (ProgressBar) findViewById(R.id.address_progress);
mConnectionState = (TextView) findViewById(R.id.text_connection_state);
mConnectionStatus = (TextView) findViewById(R.id.text_connection_status);
// Create a new global location parameters object
mLocationRequest = LocationRequest.create();
/*
* Set the update interval
*/
mLocationRequest.setInterval(LocationUtils.UPDATE_INTERVAL_IN_MILLISECONDS);
// Use high accuracy
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
// Set the interval ceiling to one minute
mLocationRequest.setFastestInterval(LocationUtils.FAST_INTERVAL_CEILING_IN_MILLISECONDS);
// Note that location updates are off until the user turns them on
mUpdatesRequested = false;
// Open Shared Preferences
mPrefs = getSharedPreferences(LocationUtils.SHARED_PREFERENCES, Context.MODE_PRIVATE);
// Get an editor
mEditor = mPrefs.edit();
mLocationClient = new LocationClient(this, this, this);
}
@Override
public void onStop() {
// If the client is connected
if (mLocationClient.isConnected()) {
stopPeriodicUpdates();
}
// After disconnect() is called, the client is considered "dead".
mLocationClient.disconnect();
super.onStop();
}
@Override
public void onPause() {
// Save the current setting for updates
mEditor.putBoolean(LocationUtils.KEY_UPDATES_REQUESTED, mUpdatesRequested);
mEditor.commit();
super.onPause();
}
@Override
public void onStart() {
super.onStart();
/*
* Connect the client. Don't re-start any requests here;
* instead, wait for onResume()
*/
mLocationClient.connect();
}
/*
* Called when the system detects that this Activity is now visible.
*/
@Override
public void onResume() {
super.onResume();
// If the app already has a setting for getting location updates, get it
if (mPrefs.contains(LocationUtils.KEY_UPDATES_REQUESTED)) {
mUpdatesRequested = mPrefs.getBoolean(LocationUtils.KEY_UPDATES_REQUESTED, false);
// Otherwise, turn off location updates until requested
} else {
mEditor.putBoolean(LocationUtils.KEY_UPDATES_REQUESTED, false);
mEditor.commit();
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
// Choose what to do based on the request code
switch (requestCode) {
// If the request code matches the code sent in onConnectionFailed
case LocationUtils.CONNECTION_FAILURE_RESOLUTION_REQUEST :
switch (resultCode) {
// If Google Play services resolved the problem
case Activity.RESULT_OK:
// Log the result
Log.d(LocationUtils.APPTAG, getString(R.string.resolved));
// Display the result
mConnectionState.setText(R.string.connected);
mConnectionStatus.setText(R.string.resolved);
break;
// If any other result was returned by Google Play services
default:
// Log the result
Log.d(LocationUtils.APPTAG, getString(R.string.no_resolution));
// Display the result
mConnectionState.setText(R.string.disconnected);
mConnectionStatus.setText(R.string.no_resolution);
break;
}
// If any other request code was received
default:
// Report that this Activity received an unknown requestCode
Log.d(LocationUtils.APPTAG,
getString(R.string.unknown_activity_request_code, requestCode));
break;
}
}
private boolean servicesConnected() {
// Check that Google Play services is available
int resultCode =
GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
// If Google Play services is available
if (ConnectionResult.SUCCESS == resultCode) {
// In debug mode, log the status
Log.d(LocationUtils.APPTAG, getString(R.string.play_services_available));
// Continue
return true;
// Google Play services was not available for some reason
} else {
// Display an error dialog
Dialog dialog = GooglePlayServicesUtil.getErrorDialog(resultCode, this, 0);
if (dialog != null) {
ErrorDialogFragment errorFragment = new ErrorDialogFragment();
errorFragment.setDialog(dialog);
errorFragment.show(getSupportFragmentManager(), LocationUtils.APPTAG);
}
return false;
}
}
public void getLocation(View v) {
// If Google Play Services is available
if (servicesConnected()) {
// Get the current location
Location currentLocation = mLocationClient.getLastLocation();
// Display the current location in the UI
mLatLng.setText(LocationUtils.getLatLng(this, currentLocation));
}
}
/**
* Invoked by the "Get Address" button.
* Get the address of the current location, using reverse geocoding. This only works if
* a geocoding service is available.
*
* @param v The view object associated with this method, in this case a Button.
*/
// For Eclipse with ADT, suppress warnings about Geocoder.isPresent()
@SuppressLint("NewApi")
public void getAddress(View v) {
// In Gingerbread and later, use Geocoder.isPresent() to see if a geocoder is available.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD && !Geocoder.isPresent()) {
// No geocoder is present. Issue an error message
Toast.makeText(this, R.string.no_geocoder_available, Toast.LENGTH_LONG).show();
return;
}
if (servicesConnected()) {
// Get the current location
Location currentLocation = mLocationClient.getLastLocation();
// Turn the indefinite activity indicator on
mActivityIndicator.setVisibility(View.VISIBLE);
// Start the background task
(new LocationActivity.GetAddressTask(this)).execute(currentLocation);
}
}
/**
* Invoked by the "Start Updates" button
* Sends a request to start location updates
*
* @param v The view object associated with this method, in this case a Button.
*/
public void startUpdates(View v) {
mUpdatesRequested = true;
if (servicesConnected()) {
startPeriodicUpdates();
}
}
/**
* Invoked by the "Stop Updates" button
* Sends a request to remove location updates
* request them.
*
* @param v The view object associated with this method, in this case a Button.
*/
public void stopUpdates(View v) {
mUpdatesRequested = false;
if (servicesConnected()) {
stopPeriodicUpdates();
}
}
/*
* Called by Location Services when the request to connect the
* client finishes successfully. At this point, you can
* request the current location or start periodic updates
*/
@Override
public void onConnected(Bundle bundle) {
mConnectionStatus.setText(R.string.connected);
if (mUpdatesRequested) {
startPeriodicUpdates();
}
}
/*
* Called by Location Services if the connection to the
* location client drops because of an error.
*/
@Override
public void onDisconnected() {
mConnectionStatus.setText(R.string.disconnected);
}
/*
* Called by Location Services if the attempt to
* Location Services fails.
*/
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
/*
* Google Play services can resolve some errors it detects.
* If the error has a resolution, try sending an Intent to
* start a Google Play services activity that can resolve
* error.
*/
if (connectionResult.hasResolution()) {
try {
// Start an Activity that tries to resolve the error
connectionResult.startResolutionForResult(
this,
LocationUtils.CONNECTION_FAILURE_RESOLUTION_REQUEST);
/*
* Thrown if Google Play services canceled the original
* PendingIntent
*/
} catch (IntentSender.SendIntentException e) {
// Log the error
e.printStackTrace();
}
} else {
// If no resolution is available, display a dialog to the user with the error.
showErrorDialog(connectionResult.getErrorCode());
}
}
/**
* Report location updates to the UI.
*
* @param location The updated location.
*/
@Override
public void onLocationChanged(Location location) {
// Report to the UI that the location was updated
mConnectionStatus.setText(R.string.location_updated);
// In the UI, set the latitude and longitude to the value received
mLatLng.setText(LocationUtils.getLatLng(this, location));
}
/**
* In response to a request to start updates, send a request
* to Location Services
*/
private void startPeriodicUpdates() {
mLocationClient.requestLocationUpdates(mLocationRequest, this);
mConnectionState.setText(R.string.location_requested);
}
/**
* In response to a request to stop updates, send a request to
* Location Services
*/
private void stopPeriodicUpdates() {
mLocationClient.removeLocationUpdates(this);
mConnectionState.setText(R.string.location_updates_stopped);
}
/**
* An AsyncTask that calls getFromLocation() in the background.
* The class uses the following generic types:
* Location - A {@link android.location.Location} object containing the current location,
* passed as the input parameter to doInBackground()
* Void - indicates that progress units are not used by this subclass
* String - An address passed to onPostExecute()
*/
protected class GetAddressTask extends AsyncTask<Location, Void, String> {
// Store the context passed to the AsyncTask when the system instantiates it.
Context localContext;
// Constructor called by the system to instantiate the task
public GetAddressTask(Context context) {
// Required by the semantics of AsyncTask
super();
// Set a Context for the background task
localContext = context;
}
/**
* Get a geocoding service instance, pass latitude and longitude to it, format the returned
* address, and return the address to the UI thread.
*/
@Override
protected String doInBackground(Location... params) {
/*
* Get a new geocoding service instance, set for localized addresses. This example uses
* android.location.Geocoder, but other geocoders that conform to address standards
* can also be used.
*/
Geocoder geocoder = new Geocoder(localContext, Locale.getDefault());
// Get the current location from the input parameter list
Location location = params[0];
// Create a list to contain the result address
List <Address> addresses = null;
// Try to get an address for the current location. Catch IO or network problems.
try {
/*
* Call the synchronous getFromLocation() method with the latitude and
* longitude of the current location. Return at most 1 address.
*/
addresses = geocoder.getFromLocation(location.getLatitude(),
location.getLongitude(), 1
);
// Catch network or other I/O problems.
} catch (IOException exception1) {
// Log an error and return an error message
Log.e(LocationUtils.APPTAG, getString(R.string.IO_Exception_getFromLocation));
// print the stack trace
exception1.printStackTrace();
// Return an error message
return (getString(R.string.IO_Exception_getFromLocation));
// Catch incorrect latitude or longitude values
} catch (IllegalArgumentException exception2) {
// Construct a message containing the invalid arguments
String errorString = getString(
R.string.illegal_argument_exception,
location.getLatitude(),
location.getLongitude()
);
// Log the error and print the stack trace
Log.e(LocationUtils.APPTAG, errorString);
exception2.printStackTrace();
//
return errorString;
}
// If the reverse geocode returned an address
if (addresses != null && addresses.size() > 0) {
// Get the first address
Address address = addresses.get(0);
// Format the first line of address
String addressText = getString(R.string.address_output_string,
// If there's a street address, add it
address.getMaxAddressLineIndex() > 0 ?
address.getAddressLine(0) : "",
// Locality is usually a city
address.getLocality(),
// The country of the address
address.getCountryName()
);
// Return the text
return addressText;
// If there aren't any addresses, post a message
} else {
return getString(R.string.no_address_found);
}
}
/**
* A method that's called once doInBackground() completes. Set the text of the
* UI element that displays the address. This method runs on the UI thread.
*/
@Override
protected void onPostExecute(String address) {
// Turn off the progress bar
mActivityIndicator.setVisibility(View.GONE);
// Set the address in the UI
mAddress.setText(address);
}
}
/**
* Show a dialog returned by Google Play services for the
* connection error code
*
* @param errorCode An error code returned from onConnectionFailed
*/
private void showErrorDialog(int errorCode) {
// Get the error dialog from Google Play services
Dialog errorDialog = GooglePlayServicesUtil.getErrorDialog(
errorCode,
this,
LocationUtils.CONNECTION_FAILURE_RESOLUTION_REQUEST);
// If Google Play services can provide an error dialog
if (errorDialog != null) {
// Create a new DialogFragment in which to show the error dialog
ErrorDialogFragment errorFragment = new ErrorDialogFragment();
// Set the dialog in the DialogFragment
errorFragment.setDialog(errorDialog);
// Show the error dialog in the DialogFragment
errorFragment.show(getSupportFragmentManager(), LocationUtils.APPTAG);
}
}
/**
* Define a DialogFragment to display the error dialog generated in
* showErrorDialog.
*/
public static class ErrorDialogFragment extends DialogFragment {
// Global field to contain the error dialog
private Dialog mDialog;
/**
* Default constructor. Sets the dialog field to null
*/
public ErrorDialogFragment() {
super();
mDialog = null;
}
/**
* Set the dialog to display
*
* @param dialog An error dialog
*/
public void setDialog(Dialog dialog) {
mDialog = dialog;
}
/*
* This method must return a Dialog to the DialogFragment.
*/
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
return mDialog;
}
}
}
来源：https://stackoverflow.com/questions/17505344/android-starting-another-activity-or-calling-a-method-from-another-class-using