maketext不適用於參數

Question

我正在編寫一個應用程序以基於緯度和經度顯示用戶的當前地址，但是我在Toast.makeText(this, "No address found try again", Toast.LENGTH_SHORT).show();上的此代碼中遇到一個錯誤Toast.makeText(this, "No address found try again", Toast.LENGTH_SHORT).show(); 這意味着toast類型的makeText不適用於參數。 我無法解決此錯誤。 有幫助嗎？ 我正在嘗試在TextView中顯示用戶地址，但是我不確定我是否做得很好，否則將來可能會出現運行時錯誤。 這是我的主要活動Java代碼：

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GoogleApiAvailability;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.GoogleApiClient.ConnectionCallbacks;
import com.google.android.gms.common.api.GoogleApiClient.OnConnectionFailedListener;
import com.google.android.gms.location.LocationServices;
import android.app.Activity;
import android.app.Dialog;
import android.app.DialogFragment;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.IntentSender.SendIntentException;
import android.location.Geocoder;
import android.location.Location;
import android.os.Bundle;
import android.os.Handler;
import android.os.ResultReceiver;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity implements OnItemSelectedListener, ConnectionCallbacks, OnConnectionFailedListener{
    private static final int REQUEST_RESOLVE_ERROR = 1001;
    private static final String DIALOG_ERROR = "dialog_error";
    private static final String STATE_RESOLVING_ERROR = "resolving_error";
    GoogleApiClient mGoogleApiClient;
    protected Location mLastLocation;
    private boolean mResolvingError=false;
    private AddressResultReceiver mResultReceiver;
    // Request code to use when launching the resolution activity
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Spinner spinner = (Spinner) findViewById(R.id.shop_category);
        // Create an ArrayAdapter using the string array and a default spinner layout
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
                R.array.shop_category, android.R.layout.simple_spinner_item);
        // Specify the layout to use when the list of choices appears
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        // Apply the adapter to the spinner
        spinner.setAdapter(adapter);
        spinner.setOnItemSelectedListener(this);
        if (mGoogleApiClient == null) {
            mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
        }
        mResolvingError = savedInstanceState != null
                && savedInstanceState.getBoolean(STATE_RESOLVING_ERROR, false);
    }
    @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();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        // TODO Auto-generated method stub
        TextView mytext = (TextView) view;
        Toast.makeText(this,"You selected "+mytext.getText(),Toast.LENGTH_SHORT).show();    
    }
    @Override
    public void onNothingSelected(AdapterView<?> parent) {
        // TODO Auto-generated method stub      
    }
    protected void startIntentService() {
        Intent intent = new Intent(this, FetchAddressIntentService.class);
        intent.putExtra(Constants.RECEIVER, mResultReceiver);
        intent.putExtra(Constants.LOCATION_DATA_EXTRA, mLastLocation);
        startService(intent);
    }
    @Override
    public void onConnected(Bundle arg0) {
        boolean mAddressRequested=false;
        // TODO Auto-generated method stub
        TextView myLatitude = (TextView)findViewById(R.id.lat_value);
        TextView myLongitude = (TextView)findViewById(R.id.lang_value);
        mLastLocation = LocationServices.FusedLocationApi.getLastLocation(
                mGoogleApiClient);
        if (mLastLocation != null) {
            myLatitude.setText(String.valueOf(mLastLocation.getLatitude()));
            myLongitude.setText(String.valueOf(mLastLocation.getLongitude()));
         if (!Geocoder.isPresent()) {
                Toast.makeText(this, R.string.no_geocoder_available,
                        Toast.LENGTH_LONG).show();
                return;
            }
         else{
             mAddressRequested=true;
            if (mAddressRequested) {
                startIntentService();
            }
         }
        }
    }
    @Override
    public void onConnectionSuspended(int arg0) {
        // TODO Auto-generated method stub  
    }
    @Override
    public void onConnectionFailed(ConnectionResult result) {
        // TODO Auto-generated method stub
        if (mResolvingError) {
            Toast.makeText(this, "Resolving errors", Toast.LENGTH_SHORT).show();
          return;
        } else if (result.hasResolution()) {
            try {
                mResolvingError = true;
                result.startResolutionForResult(this, REQUEST_RESOLVE_ERROR);
            } catch (SendIntentException e) {
                // There was an error with the resolution intent. Try again.
                mGoogleApiClient.connect();
            }
        } else {
            // Show dialog using GoogleApiAvailability.getErrorDialog()
            showErrorDialog(result.getErrorCode());
            mResolvingError = true;
        }
    }
    private void showErrorDialog(int errorCode) {
        // Create a fragment for the error dialog
        ErrorDialogFragment dialogFragment = new ErrorDialogFragment();
        // Pass the error that should be displayed
        Bundle args = new Bundle();
        args.putInt(DIALOG_ERROR, errorCode);
        dialogFragment.setArguments(args);
        dialogFragment.show(getFragmentManager(), "errordialog");
    }
    public void onDialogDismissed() {
        mResolvingError = false;
    }
    public static class ErrorDialogFragment extends DialogFragment {
        public ErrorDialogFragment() { }

        @Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {
            // Get the error code and retrieve the appropriate dialog
            int errorCode = this.getArguments().getInt(DIALOG_ERROR);
            return GoogleApiAvailability.getInstance().getErrorDialog(
                    this.getActivity(), errorCode, REQUEST_RESOLVE_ERROR);
        }

        @Override
        public void onDismiss(DialogInterface dialog) {
            ((MainActivity) getActivity()).onDialogDismissed();
        }
    }
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == REQUEST_RESOLVE_ERROR) {
            mResolvingError = false;
            if (resultCode == RESULT_OK) {
                if (!mGoogleApiClient.isConnecting() &&
                        !mGoogleApiClient.isConnected()) {
                    mGoogleApiClient.connect();
                }
            }
            }
        }
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putBoolean(STATE_RESOLVING_ERROR, mResolvingError);
    }
    protected void onStart() {
        mGoogleApiClient.connect();
        super.onStart();
    }

    protected void onStop() {
        mGoogleApiClient.disconnect();
        super.onStop();
    }
    class AddressResultReceiver extends ResultReceiver {
        public AddressResultReceiver(Handler handler) {
            super(handler);
        }
        @Override
        protected void onReceiveResult(int resultCode, Bundle resultData) {
            // Display the address string
            // or an error message sent from the intent service.
           String mAddressOutput = resultData.getString(Constants.RESULT_DATA_KEY);

            // Show a toast message if an address was found.
            if (resultCode == Constants.SUCCESS_RESULT) {
                TextView myaddress=(TextView) findViewById(R.id.myaddress);
                myaddress.setText(mAddressOutput);
            }
            else{
                Toast.makeText(this, "No address found try again", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

先感謝您。

Answer 1

用MainActivity.this代替this ，作為makeText()調用的第一個參數。 this是您的AddressResultReceiver內部類的實例。 這不是您的活動，並且makeText()需要一個Context ，例如Activity 。

Answer 2

使用getApplicationContext()代替this 。 采用：

Toast.makeText(getApplicationContext(), "message", Toast.LENGTH_SHORT).show();

this是指AddressResultReceiver這是不是子類Context 。

Toast.makeText()需要Context 。