Problem mit Android ListView

[Lucaaa]

Hallo!
Ich habe eine ListView, die alle Audiodateien anzeigen soll. Problem: es wird gar nichts angezeigt (Liste ist leer).
Wo liegt der Fehler?

MainActivity.java

package musicplayer.ludevstudio.com.musikplayer;

import android.Manifest;
import android.app.Activity;
import android.content.ContentResolver;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.ActivityCompat;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;
import android.widget.Toast;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {


    public ArrayList<Song> songs;


    @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.addDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);


        checkPermissions();

    }

    @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();

        if (id == R.id.nav_camera) {
            // Handle the camera action
        } else if (id == R.id.nav_gallery) {

        } else if (id == R.id.nav_slideshow) {

        } else if (id == R.id.nav_manage) {

        } 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;
    }

    // Check for permissions if there are granted or not
    public boolean checkPermissions() {
        if(ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
            searchAndShowSongs();

        } else {
            ActivityCompat.requestPermissions(this, new String[] { Manifest.permission.READ_EXTERNAL_STORAGE }, 1);

        }
    return false;

    }

    // React to Permissions Dialog
    public void onRequestPermissionsResult(int requestCode, String permissions[], int[] ergebnis) {
        if (requestCode == 1) {
            if (ergebnis.length > 0
                    && ergebnis[0] == PackageManager.PERMISSION_GRANTED) {

            } else {

            }
            return;
        }
    }


    public void searchAndShowSongs() {
        songs = new ArrayList<Song>();

        ContentResolver musicResolver = getContentResolver();
        Uri musicUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
        Cursor songCursor = musicResolver.query(musicUri, null, null, null, null);

        if(songCursor==null && songCursor.moveToFirst()) {
            int titlelColumn = songCursor.getColumnIndex(MediaStore.Audio.Media.TITLE);

            do {
                String thisTitle = songCursor.getString(titlelColumn);
                songs.add(new Song(thisTitle));

            } while (songCursor.moveToNext());


            songs.add(new Song("Fail of Searching"));

        }

        SongAdapter liedAdapter = new SongAdapter(this, songs);
        ListView liedListView = (ListView)findViewById(R.id.SongListView);
        liedListView.setAdapter(liedAdapter);

        Toast.makeText(this, "Test", Toast.LENGTH_SHORT).show();

    }


}

SongAdapter.Java (Der ListAdapter)

package musicplayer.ludevstudio.com.musikplayer;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.RelativeLayout;
import android.widget.TextView;
import java.util.ArrayList;


public class SongAdapter extends BaseAdapter {

    private ArrayList<Song> songs;
    private LayoutInflater liedInf;

    public SongAdapter(Context c, ArrayList<Song> songs){
        this.songs = songs;
        liedInf = LayoutInflater.from(c);
    }

    @Override
    public int getCount() {
        return songs.size();
    }

    @Override
    public Object getItem(int arg0) {
        return null;
    }

    @Override
    public long getItemId(int arg0) {
        return arg0;
    }

    @Override
    public View getView(int arg0, View arg1, ViewGroup arg2) {

        RelativeLayout songLay = (RelativeLayout)liedInf.inflate(R.layout.songlistview_entrees, arg2, false);

        TextView songView = (TextView)songLay.findViewById(R.id.LiedTitel);

        Song momentanesLied = songs.get(arg0);

        songView.setText(momentanesLied.getTitel());

        songLay.setTag(arg0);

        return songLay;
    }
}

Song.java

package musicplayer.ludevstudio.com.musikplayer;

public class Song {
    private String titel =  "";


    public Song(String title) {
        this.titel = title;
    }



    public String getTitel() {
        return titel;
    }

    public void setTitel(String titel) {
        this.titel = titel;
    }



}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout 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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />



    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer" />

</android.support.v4.widget.DrawerLayout>

content_main.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/SongListView"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:visibility="visible"
        android:layout_alignParentStart="true" />


</RelativeLayout>

app_bar_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.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        app:srcCompat="@android:drawable/ic_dialog_email" />

    <include
        layout="@layout/content_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="top"
        />


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

songlistview_entrees.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="Medium Text"
        android:id="@+id/LiedTitel"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
</RelativeLayout>

 

[truesoul]

Hallo.

Was wäre wenn du denn Debugger anschmeisst? Oder ein paar Log ausgaben einbaust?

 

[mihe7]

 if(songCursor==null && songCursor.moveToFirst()) {

Ich würde es mal mit songCursor != null probieren.