Android: 我在操作栏中设置了一些图标，但它们没有显示在我的设备上

Question

我想在我的操作栏中添加一些操作。在我的设计预览中显示了图标，但在我的设备上操作栏中没有显示图标。我必须更改什么才能在操作栏中显示图标？

menu_main.xml

<menu xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android" >

    <item
        android:id="@+id/action_refresh"
        android:orderInCategory="100"
        android:icon="@android:drawable/ic_menu_mylocation"
        android:title="Refresh"
        app:showAsAction="always" />
    <item
        android:id="@+id/action_settings"
        android:title="Settings">
    </item>

</menu>

MainActivity.java

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu_main, menu);
        return true;
    }

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay" />

    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_main" />



</android.support.design.widget.CoordinatorLayout>

MainActivity.java:

package com.example.myApp;

import java.io.IOException;
import java.util.Calendar;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.content.pm.PackageManager;
import android.graphics.Color;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Gravity;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MainActivity extends AppCompatActivity
implements View.OnClickListener {

    private LocationManager locationManager = null;
    private LocationListener locationListener = null;
    private Button btnGetLocation = null;
    private TextView v_longitude = null;
    private TextView v_latitude = null;
    private TextView v_location = null;
    private TextView v_speed = null;
    private TextView v_altitude = null;
    private TextView v_sat = null;
    private TextView v_gps_status = null;
    private TextView v_update_status = null;
    String longitude = "";
    String latitude = "";
    String location = "";
    String speed = "";
    String altitude = "";
    String sat_nr = "";
    String myOrt = "";
    String myBeschreibung = "";
    Button button3;

    ImageView imageView;

    private JsonPlaceHolderApi jsonPlaceHolderApi;

    private Toolbar toolbar;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        toolbar =  findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); //portrait mode
        v_longitude = (TextView) findViewById(R.id.Lon_view);
        v_latitude = (TextView) findViewById(R.id.Lat_view);
        v_location = (TextView) findViewById(R.id.Loc_view);
        v_speed = (TextView) findViewById(R.id.Spd_view);
        v_altitude = (TextView) findViewById(R.id.Alt_view);
        v_sat = (TextView) findViewById(R.id.Sat_view);
        v_gps_status = (TextView) findViewById(R.id.Gps_status);
        v_update_status = (TextView) findViewById(R.id.Update_status);

        //---------------------------------------------------------
        // Neu: mehrere Buttons
        Button button1 = findViewById(R.id.button);
        Button button2 = findViewById(R.id.button2);
        button3 = findViewById(R.id.button3);
        button3.setVisibility(View.GONE);
        Button deleteOrt = findViewById(R.id.btnDeleteOrt);
        Button deleteBeschreibung = findViewById(R.id.btnDeleteBeschreibung);


        button1.setOnClickListener(this);
        button2.setOnClickListener(this);

        button3.setOnClickListener(this);
        deleteOrt.setOnClickListener(this);
        deleteBeschreibung.setOnClickListener(this);
        //---------------------------------------------------------

        //btnGetLocation = (Button) findViewById(R.id.button);
        //btnGetLocation.setOnClickListener(this);
        locationManager = (LocationManager)
                getSystemService(Context.LOCATION_SERVICE);
        button1.performClick();

        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("http://myBaseURL.de/api/mypost.php/")
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        jsonPlaceHolderApi = retrofit.create(JsonPlaceHolderApi.class);
        //getEntries();
        //createEntry();

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu_main, menu);
        return true;
    }



    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button:
                //Check if GPS is enabled
                locationListener = new APPLocationListener();
                if (ContextCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) ==
                        PackageManager.PERMISSION_GRANTED) {
                    v_gps_status.setText("Wait for signal");
                    v_gps_status.setTextColor(Color.parseColor("#0066ff"));
                    locationManager.requestLocationUpdates(LocationManager
                            .GPS_PROVIDER, 5000, 10, locationListener);
                } else {
                    v_gps_status.setText("No GPS-Access!!!");
                    v_gps_status.setTextColor(Color.parseColor("#ff0000"));
                }
                Toast.makeText(this, "Refresh-Button clicked", Toast.LENGTH_SHORT).show();
                break;

            case R.id.button2:

                //---------------------------------------------------------------------
                // Ort und Beschreibung werden nach Touch auf den Send-Button eingelesen
                EditText etO = (EditText)findViewById(R.id.editOrt);
                myOrt = (etO.getText().toString());
                //
                EditText etB = (EditText)findViewById(R.id.editBeschreibung);
                myBeschreibung = (etB.getText().toString());
                //Log.d("DEBUG", "eingabe_click = " + myOrt );
                // --------------------------------------------------------------------

                createEntry();
                Toast.makeText(this, "Daten werden gesendet", Toast.LENGTH_SHORT).show();
                break;

            case R.id.btnDeleteOrt:
                //---------------------------------------------------------------------
                // Eintrag in Ort zurücksetzen
                EditText etO2 = (EditText)findViewById(R.id.editOrt);
                etO2.setText("", TextView.BufferType.EDITABLE);
                myOrt = "";
                break;

            case R.id.btnDeleteBeschreibung:
                //---------------------------------------------------------------------
                // Eintrag in Beschreibung zurücksetzen
                EditText etB2 = (EditText)findViewById(R.id.editBeschreibung);
                etB2.setText("", TextView.BufferType.EDITABLE);
                myBeschreibung = "";
                break;

            case R.id.button3:
                //---------------------------------------------------------------------
                // Activity Entry aufrufen
                openOrte();

                break;
        }


    }

    //-----------------------------------------------------------------------------------------------
    // Methode, um 2. Activity "Orte" zu öffnen
    private void openOrte() {
        Log.d("DEBUG", "lat = " + latitude );
        Log.d("DEBUG", "lon = " + longitude );

        // Parameter an andere Activity übergeben: (
        // In order to pass the parameters you create new intent and put a parameter map:
        Intent myIntent = new Intent (this,Orte.class);
        myIntent.putExtra("paramLatitude",latitude);
        myIntent.putExtra("paramLongitude",longitude);
        startActivity(myIntent);



//        Uri gmmIntentUri = Uri.parse("google.navigation:q=46.74015166666666,17.648755");
//        Intent mapIntent = new Intent(Intent.ACTION_VIEW, gmmIntentUri);
//        mapIntent.setPackage("com.google.android.apps.maps");
//        startActivity(mapIntent);


//
       }
    //-----------------------------------------------------------------------------------------------

    private class APPLocationListener implements LocationListener {
        @Override
        public void onLocationChanged(Location loc) {
            //Try to get city name
            String city_name = null;
            Geocoder geocoder = new Geocoder(getBaseContext(),Locale.getDefault());
            List<Address> addresses;
            try {
                addresses = geocoder.getFromLocation(loc.getLatitude(), loc.getLongitude(), 1);
                if (addresses.size() > 0)
                    city_name = addresses.get(0).getAddressLine(0);

                // Geocoder geocoder = new Geocoder(this, Locale.getDefault());
                // List<Address> addresses = geocoder.getFromLocation(MyLat, MyLong, 1);
                // String cityName = addresses.get(0).getAddressLine(0);
                // String stateName = addresses.get(0).getAddressLine(1);
                // String countryName = addresses.get(0).getAddressLine(2);

            } catch (IOException e) {
                city_name = "unknown";
                e.printStackTrace();
            }
            latitude = "" + loc.getLatitude(); //Get latitude
            longitude = "" + loc.getLongitude(); //Get longitude
            location = "" + city_name; //Get city name

            speed = "" + loc.getSpeed()*3.6 + " km/h"; //Get speed in km/h

            altitude = "" + loc.getAltitude() + " m über nn"; //Get height in meters
            sat_nr = "" + loc.getExtras().getInt("Satelliten"); //available satellites
            v_latitude.setText(latitude);
            v_longitude.setText(longitude);
            v_location.setText(location);
            v_speed.setText(speed);
            v_altitude.setText(altitude);
            v_sat.setText(sat_nr);
            v_gps_status.setText("GPS working");
            v_gps_status.setTextColor(Color.parseColor("#33cc33"));
            v_update_status.setText("Last update: " + myDatetime());

            // Button3 sichtbar machen
            //button3.setVisibility(View.VISIBLE);
            button3.setVisibility(View.VISIBLE);
            imageView = (ImageView) findViewById(R.id.action_liste);
            imageView.setVisibility(View.VISIBLE);
            invalidateOptionsMenu();

            //createPost(1);
        }



        @Override
        public void onProviderDisabled(String provider) {
            // TODO Auto-generated method stub
        }
        @Override
        public void onProviderEnabled(String provider) {
            // TODO Auto-generated method stub
        }
        @Override
        public void onStatusChanged(String provider,
                                    int status, Bundle extras) {
            // TODO Auto-generated method stub
        }
    }

    private void createEntry() {
        Post post;
        //if (Aufruf == 1) {
            post = new Post(myDatetime(), longitude, latitude, location, altitude, sat_nr, myOrt, myBeschreibung);
        //} else {
         //   post = new Post(myDatetime(), "", "", "NEW", "", "");
        //}

        Call<Post> call = jsonPlaceHolderApi.createPost(post);

        call.enqueue(new Callback<Post>() {
            @Override
            public void onResponse(Call<Post> call, Response<Post> response) {

                // HTTP-GET-REQUEST nicht erfolgreich
                if (!response.isSuccessful()) {
                    toastMsg("is nopt successful");
                    return;
                }

                // HTTP-GET-REQUEST nicht erfolgreich
                toastMsg(response.toString());
            }

            // HTTP-GET-REQUEST nicht erfolgreich
            @Override
            public void onFailure(Call<Post> call, Throwable t) {
                toastMsg("Schwerer Fehler");
            }
        });
    }



    public void toastMsg(String msg) {
        Toast toast = Toast.makeText(this, msg, Toast.LENGTH_LONG);
        toast.setGravity(Gravity.CENTER|Gravity.CENTER, 0, 100);
        toast.show();
    }

    public String myDatetime() {
        Calendar c = Calendar.getInstance(); //Get time on system
        String myDatetime = c.get(Calendar.HOUR_OF_DAY) + ":" +
                c.get(Calendar.MINUTE) + ":" + c.get(Calendar.SECOND);
        return myDatetime;
    }



}

Answer 1

您没有初始化工具栏。在 setSupportActionBar(toolbar)

上方添加以下行

toolbar =  findViewById(R.id.toolbar);

Answer 2

您必须在附加到操作栏之前初始化工具栏

private Toolbar toolbar;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    ....

}

Android: 我在操作栏中设置了一些图标，但它们没有显示在我的设备上

Android: I set some icons in the actionbar, but they were not shown on my device

java

android

android-actionbar

android-actionbar-compat