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Wenn ich versuche, meine app diese besondere Aktivität auszuführen: -Wie Sie einen Rückruf Fehler
package com.justforyou.bestnarutosongs;
import android.content.Context;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.WindowManager;
import android.widget.AdapterView;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.SeekBar;
import android.widget.TextView;
import java.util.ArrayList;
public class SongsListActivity extends AppCompatActivity //implements View.OnClickListener {
public ImageButton P_and_P = (ImageButton) findViewById(R.id.P_and_P);
public ImageButton Stop = (ImageButton) findViewById(R.id.imageButton5);
public TextView NameD = (TextView) findViewById(R.id.textView3);
public TextView RateD = (TextView) findViewById(R.id.textView4);
public SeekBar seek_bar = (SeekBar) findViewById(R.id.seekBar);
public boolean IsPaused = false;
public int Old_Song = -326523;
private MediaPlayer mediaplayer;
private AudioManager mAudioManager;
public Handler seekHandler = new Handler();
private AudioManager.OnAudioFocusChangeListener mOnAudioFocusChangeListener = new AudioManager.OnAudioFocusChangeListener()
{
@Override
public void onAudioFocusChange(int focusChange){
if(focusChange == AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK || focusChange == AudioManager.AUDIOFOCUS_LOSS_TRANSIENT){
mediaplayer.pause();
mediaplayer.seekTo(0);
}
else if(focusChange == AudioManager.AUDIOFOCUS_GAIN){
mediaplayer.start();
}
else if(focusChange == AudioManager.AUDIOFOCUS_LOSS){
if(mediaplayer != null)
{
mediaplayer.release();
mediaplayer = null;
}
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_songs_list);
seekUpdation();
mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
final ArrayList<Songs> Song = new ArrayList<>();
Song.add(new Songs("Anger", "Rate: 4.5", R.raw.anger, R.drawable.anger));
Song.add(new Songs("Daylight Of Konoha", "Rate: 4.7", R.raw.d_o_k, R.drawable.d_o_k));
Song.add(new Songs("Experienced Many Battles", "Rate: 4.0", R.raw.experienced_many_battles, R.drawable.e_m_b));
Song.add(new Songs("Gekiha", "Rate: 4.0", R.raw.gekiha, R.drawable.gekiha));
Song.add(new Songs("Genshi", "Rate: 3.0", R.raw.genshi, R.drawable.genshi));
Song.add(new Songs("Girei", "Rate: 4.5", R.raw.girei, R.drawable.girei));
Song.add(new Songs("Hidan", "Rate: 3.0", R.raw.hidan, R.drawable.hidan));
Song.add(new Songs("HomeComing", "Rate: 3.0", R.raw.homecoming, R.drawable.homecoming));
Song.add(new Songs("Naruto Main Theme", "Rate: 5.0", R.raw.naruto_main_theme, R.drawable.narutomt));
Song.add(new Songs("Saika", "Rate: 4.5", R.raw.saika, R.drawable.saika));
Song.add(new Songs("Senya(Itachi's Theme)", "Rate: 5.0", R.raw.senya, R.drawable.senya));
Song.add(new Songs("Shirotsumekusa", "Rate: 3.0", R.raw.shirotsumekusa, R.drawable.shirot));
Song.add(new Songs("Turn Over", "Rate: 4.5", R.raw.turn_over, R.drawable.turn_over));
P_and_P.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view)
{
if(mediaplayer != null)
{
if(!mediaplayer.isPlaying() || IsPaused)
{
P_and_P.setImageResource(R.drawable.ic_play_arrow_white_48dp);
IsPaused = false;
int result = mAudioManager.requestAudioFocus(mOnAudioFocusChangeListener, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);
if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
mediaplayer.start();
mediaplayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
@Override
public void onCompletion(MediaPlayer mediaPlayer) {
if (mediaplayer != null) {
mediaplayer.release();
mediaplayer = null;
mAudioManager.abandonAudioFocus(mOnAudioFocusChangeListener);
}
}
});
}
}
else
{
P_and_P.setImageResource(R.drawable.ic_pause_white_48dp);////////////////////////////////////////////////////////////////////
IsPaused = true;
mediaplayer.pause();
}
}
}
});
Stop.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(mediaplayer != null)
{
mediaplayer.pause();
mediaplayer.seekTo(0);
IsPaused = true;
}
}
});
SongsAdapter SongAdapter = new SongsAdapter(this, Song, R.color.Main_Color);
ListView listView = (ListView) findViewById(R.id.list_Col);
listView.setAdapter(SongAdapter);
listView.setOnItemClickListener
(new AdapterView.OnItemClickListener()
{
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l)
{
int Current_Song;
Songs song = Song.get(i);
//If mediaPlayer is not used before, this will make oldsong as present song.
if (Old_Song == -326523)
{
Old_Song = song.getSong();
}
Current_Song = song.getSong();
ImageView IVP_P = (ImageView) findViewById(R.id.P_PImage);
//If mediaPlayer is paused.
if (IsPaused)
{
//If the song paused is same as the new song.
if(Current_Song == Old_Song)
{
mediaplayer.start();
}
//If the song Paused is not the new song.
else
{
if (mediaplayer != null)
{
mediaplayer.release();
mediaplayer = null;
}
int result = mAudioManager.requestAudioFocus(mOnAudioFocusChangeListener, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);
if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
mediaplayer = mediaplayer.create(SongsListActivity.this, song.getSong());
Old_Song = song.getSong();
mediaplayer.start();
mediaplayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
@Override
public void onCompletion(MediaPlayer mediaPlayer) {
if (mediaplayer != null) {
mediaplayer.release();
mediaplayer = null;
mAudioManager.abandonAudioFocus(mOnAudioFocusChangeListener);
}
}
});
}
}
IsPaused = false;
}
else if (mediaplayer != null)
{
//If mediaPlayer is already Playing a song.
if (mediaplayer.isPlaying()) {
mediaplayer.pause();
IVP_P.setImageResource(R.drawable.ic_play_arrow_black_24dp);
IsPaused = true;
}
}
//If mediaPlayer is used for first time and if mediaPlayer is neither paused
else
{
if (mediaplayer != null)
{
mediaplayer.release();
mediaplayer = null;
}
int result = mAudioManager.requestAudioFocus(mOnAudioFocusChangeListener, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);
if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
mediaplayer = mediaplayer.create(SongsListActivity.this, song.getSong());
Old_Song = song.getSong();
mediaplayer.start();
mediaplayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
@Override
public void onCompletion(MediaPlayer mediaPlayer) {
if (mediaplayer != null) {
mediaplayer.release();
mediaplayer = null;
mAudioManager.abandonAudioFocus(mOnAudioFocusChangeListener);
}
}
});
}
}
}
}
);
}
Runnable run = new Runnable(){
@Override
public void run() {
seekUpdation();
}
};
public void seekUpdation()
{
if(mediaplayer != null) {
seek_bar.setProgress(mediaplayer.getCurrentPosition());
seekHandler.postDelayed(run, 1000);
}
}
@Override
protected void onStop() {
super.onStop();
if(mediaplayer != null)
{
mediaplayer.release();
mediaplayer = null;
}
}
}
gibt diesen Fehler: -
08-08 14:39:41.281 1730-1730/com.justforyou.bestnarutosongs E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.justforyou.bestnarutosongs, PID: 1730
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.justforyou.bestnarutosongs/com.justforyou.bestnarutosongs.SongsListActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2444)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2613)
at android.app.ActivityThread.access$800(ActivityThread.java:181)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1473)
at android.os.Handler.dispatchMessage(Handler.java:111)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5649)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference
at android.support.v7.app.AppCompatDelegateImplBase.<init>(AppCompatDelegateImplBase.java:72)
at android.support.v7.app.AppCompatDelegateImplV7.<init>(AppCompatDelegateImplV7.java:146)
at android.support.v7.app.AppCompatDelegateImplV11.<init>(AppCompatDelegateImplV11.java:28)
at android.support.v7.app.AppCompatDelegateImplV14.<init>(AppCompatDelegateImplV14.java:41)
at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:193)
at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:173)
at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:511)
at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:183)
at com.justforyou.bestnarutosongs.SongsListActivity.<init>(SongsListActivity.java:23)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1606)
at android.app.Instrumentation.newActivity(Instrumentation.java:1071)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2434)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2613)
at android.app.ActivityThread.access$800(ActivityThread.java:181)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1473)
at android.os.Handler.dispatchMessage(Handler.java:111)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5649)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)
mir jemand sagen kann, was ist Fehler verursachen? Hier ist die XML-Datei: -
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_height="match_parent"
android:layout_width="match_parent">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="0.58"
android:background="@color/Player_Color">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="2.27">
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:weightSum="1">
<ImageView
android:layout_width="100dp"
android:layout_height="100dp"
android:id="@+id/imageView" />
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="match_parent"
android:layout_height="0dp"
android:text="Please Select a Song"
android:textAppearance="?android:textAppearanceMedium"
android:textStyle="bold"
android:id="@+id/textView3"
android:layout_weight="1"
android:gravity="bottom" />
<TextView
android:layout_width="match_parent"
android:layout_height="0dp"
android:text=""
android:id="@+id/textView4"
android:layout_weight="1" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1">
<ImageButton
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:id="@+id/Repeat"
android:layout_weight="1"
android:background="@color/Player_Color"
android:src="@drawable/ic_repeat_white_48dp" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:id="@+id/Previous"
android:layout_weight="1"
android:background="@color/Player_Color"
android:src="@drawable/ic_skip_previous_white_48dp" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:id="@+id/P_and_P"
android:layout_weight="1"
android:src="@drawable/ic_play_arrow_white_48dp"
android:background="@color/Player_Color" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:id="@+id/Next"
android:layout_weight="1"
android:background="@color/Player_Color"
android:src="@drawable/ic_skip_next_white_48dp" />
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="match_parent">
<ImageButton
android:padding="11dp"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:id="@+id/imageButton5"
android:background="@color/Player_Color"
android:src="@drawable/control_stop"
android:scaleType="centerInside"
android:layout_centerVertical="true"
android:layout_alignParentStart="true" />
</RelativeLayout>
</LinearLayout>
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1">
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:weightSum="1"
android:gravity="center_vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="00:00"
android:id="@+id/textView"
android:gravity="center_vertical" />
<SeekBar
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/seekBar"
android:layout_weight="1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="00:00"
android:id="@+id/textView2"
android:gravity="center_vertical" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
</RelativeLayout>
<ListView
android:id="@+id/list_Col"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:layout_gravity="bottom"
android:drawSelectorOnTop="true"
android:orientation="vertical"
tools:context="com.justforyou.bestnarutosongs.SongsListActivity"
style="centreCrop" />
Während dieser XML-Datei zu machen, es gibt mir auch diesen Fehler: -
Sind diese zwei Fehler bezogen oder nicht. Was könnte die beste Lösung für dieses Problem sein? Jede Hilfe wird geschätzt.
Obwohl dies mein Problem gelöst hat, werden Sie mir sagen, warum das half? –
Weil findViewById-Methode ein View-Objekt benötigt. Die SetContentView-Methode stellt nur ein View-Objekt zur Verfügung. Wenn findViewById vor dem Aufruf von setContentView aufgerufen wird, kann die findViewById-Methode das View-Objekt nicht abrufen. –
Ok! Ich habe es verstanden. Danke –