java - 如何保存 mediaPlayer 状态？
问题描述
我是应用程序开发领域的初学者，但不幸的是我无法继续学习，因为我无法保存活动状态。几年前我的问题已经被另一个用户在这里问过了，但没有解决办法，所以我希望我能把它放回这里，谢谢。
我正在开发音乐播放器，播放、停止和暂停按钮有效。我的问题是，每当播放一首歌曲并且我按下后退按钮并再次打开应用程序时，这些按钮不适用于当前歌曲。
当我改变方向或在屏幕之间导航时也会发生这种情况，当我转到主屏幕并返回音乐屏幕时，即使已经播放了音乐，它也会重置所有信息，就好像我从未点击过播放一样。
有没有办法保存媒体播放器状态并让它停止播放音乐？
MainActivity.java
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Handler;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.material.bottomnavigation.BottomNavigationView;
import androidx.appcompat.app.AppCompatActivity;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;
public class MainActivity extends AppCompatActivity {
private ImageView imagePlayPause;
private TextView textCurrentTime, textTotalDuration;
private SeekBar playerSeekBar;
private MediaPlayer mediaPlayer;
private Handler handler = new Handler();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BottomNavigationView navView = findViewById(R.id.nav_view);
// Passing each menu ID as a set of Ids because each
// menu should be considered as top level destinations.
AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
R.id.navigation_mapa, R.id.navigation_casa, R.id.navigation_musica)
.build();
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
NavigationUI.setupWithNavController(navView, navController);
//seria meio que, leia aquilo que possui o ID = imagePlayPause
imagePlayPause = findViewById(R.id.imagePlayPause);
textCurrentTime = findViewById(R.id.textCurrentTime);
textTotalDuration = findViewById(R.id.textTotalDuration);
playerSeekBar = findViewById(R.id.playerSeekBar);
mediaPlayer = new MediaPlayer();
playerSeekBar.setMax(100);
imagePlayPause.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(mediaPlayer.isPlaying())
{
handler.removeCallbacks(updater);
mediaPlayer.pause();
//trocar a imgem do botão
imagePlayPause.setImageResource(R.drawable.ic_play);
}else{
mediaPlayer.start();
imagePlayPause.setImageResource(R.drawable.ic_pause);
updateSeekBar();
}
}
});
prepareMediaPlayer();
playerSeekBar.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View view, MotionEvent event) {
SeekBar seekBar = (SeekBar) view;
int playPosition = (mediaPlayer.getDuration() / 100) * seekBar.getProgress();
mediaPlayer.seekTo(playPosition);
textCurrentTime.setText(milliSecondsToTimer(mediaPlayer.getCurrentPosition()));
return false;
}
});
mediaPlayer.setOnBufferingUpdateListener(new MediaPlayer.OnBufferingUpdateListener() {
@Override
public void onBufferingUpdate(MediaPlayer mediaPlayer, int i) {
playerSeekBar.setSecondaryProgress(i);
}
});
mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
@Override
public void onCompletion(MediaPlayer mp) {
playerSeekBar.setProgress(0);
imagePlayPause.setImageResource(R.drawable.ic_play);
textCurrentTime.setText(R.string.zero);
textTotalDuration.setText(R.string.zero);
mediaPlayer.reset();
prepareMediaPlayer();
}
});
}
private void prepareMediaPlayer()
{
try {
mediaPlayer.setDataSource("https://www.youtube.com/watch?v=orJSJGHjBLI"); //URL do arquivo de musica
mediaPlayer.prepare();
textTotalDuration.setText(milliSecondsToTimer(mediaPlayer.getDuration()));
} catch (Exception exception){
Toast.makeText(this, exception.getMessage(), Toast.LENGTH_SHORT).show();
}
}
private Runnable updater = new Runnable() {
@Override
public void run() {
updateSeekBar();
long currentDuration = mediaPlayer.getCurrentPosition();
textCurrentTime.setText(milliSecondsToTimer(currentDuration));
}
};
private void updateSeekBar()
{
if(mediaPlayer.isPlaying())
{
playerSeekBar.setProgress((int) (((float) mediaPlayer.getCurrentPosition() / mediaPlayer.getDuration()) * 100));
handler.postDelayed(updater, 1000);
}
}
private String milliSecondsToTimer(long milliSeconds)
{
String timerString = "";
String secondsString;
int hours = (int)(milliSeconds / (1000 * 60 * 60));
int minutes = (int)(milliSeconds % (1000 * 60 * 60)) / (1000 * 60);
int seconds = (int)((milliSeconds % (1000 * 60 * 60)) % (1000 * 60) / 1000);
if(hours > 0)
{
timerString = hours + ":";
}
if(seconds < 10)
{
secondsString = "0" + seconds;
} else{
secondsString = "" + seconds;
}
timerString = timerString + minutes + ":" + secondsString;
return timerString;
}
}
screen_home.xml
<androidx.constraintlayout.widget.ConstraintLayout 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=".ui.music.MusicFragment">
<TextView
android:id="@+id/text_notifications"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="396dp"
android:textAlignment="center"
android:textSize="20sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintStart_toStartOf="parent" />
<ImageView
android:id="@+id/imagePlayPause"
android:layout_width="43dp"
android:layout_height="45dp"
android:layout_marginStart="28dp"
android:layout_marginTop="80dp"
android:src="@drawable/ic_play"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:ignore="contentDescription" />
<TextView
android:id="@+id/nomeMusica"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="72dp"
android:text="@string/nomeMusica"
android:textSize="16sp"
android:textStyle="bold"
app:layout_constraintStart_toEndOf="@+id/imagePlayPause"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/linhaSeparacao2"
android:layout_width="762dp"
android:layout_height="25dp"
android:layout_marginTop="40dp"
android:text="@string/separacao"
android:textColor="#212121"
app:layout_constraintBottom_toTopOf="@+id/nomeMusica"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/linhaDeSeparacao"
android:layout_width="420dp"
android:layout_height="20dp"
android:layout_marginTop="127dp"
android:layout_marginBottom="584dp"
android:text="@string/separacao"
android:textColor="#212121"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.555"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<androidx.cardview.widget.CardView
android:layout_width="94dp"
android:layout_height="92dp"
android:layout_marginStart="16dp"
android:layout_marginTop="52dp"
android:layout_marginEnd="0dp"
app:cardCornerRadius="200dp"
app:cardElevation="0dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintStart_toEndOf="@+id/nomeMusica"
app:layout_constraintTop_toTopOf="parent"
tools:ignore="MissingConstraints">
<ImageView
android:id="@+id/imgPiano"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scaleType="centerCrop"
android:src="@drawable/piano_cello"
tools:ignore="contentDescription"
/>
</androidx.cardview.widget.CardView>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="21dp"
android:gravity="center_vertical"
android:orientation="horizontal"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.399"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.149">
<TextView
android:id="@+id/textCurrentTime"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="@string/zero"
android:textColor="#212121"
android:textSize="16sp" />
<SeekBar
android:id="@+id/playerSeekBar"
android:layout_width="116dp"
android:layout_height="22dp"
android:layout_marginStart="8dp"
android:layout_marginEnd="8dp" />
<TextView
android:id="@+id/textTotalDuration"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="@string/zero"
android:textColor="#212121"
android:textSize="16sp" />
</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
AndroidManifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
package="com.example.studywithmeoficial">
<uses-permission android:name="android.permission.INTERNET"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/Theme.StudyWithMeOficial"
android:usesCleartextTraffic="true"
tools:targetApi="m">
<activity
android:name=".MainActivity"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
解决方案
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