Question

现在，我正尝试在应用程序的开头播放视频，作为欢迎问候语，我在添加控制器之前遵循了此 Video player link 。我编写了以下代码，并成功在单独的Activity中运行。

public class MainActivity extends AppCompatActivity {

private static final String VIDEO_SAMPLE = "tacoma_narrows";
private VideoView mVideoView;

@Override
protected void onStart() {
    super.onStart();

    initializePlayer();
}

@Override
protected void onStop() {
    super.onStop();

    releasePlayer();
}

@Override
protected void onPause() {
    super.onPause();

    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N) {
        mVideoView.pause();
    }
}



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mVideoView = findViewById(R.id.startingvideo);


}

private Uri getMedia(String mediaName) {
    return Uri.parse("android.resource://" + getPackageName() +
            "/raw/" + mediaName);
}
private void initializePlayer() {
    Uri videoUri = getMedia(VIDEO_SAMPLE);
    mVideoView.setVideoURI(videoUri);
    mVideoView.start();
}
private void releasePlayer() {
    mVideoView.stopPlayback();
}}

但是当我尝试在欢迎屏幕中添加相同的代码时，我收到以下消息

java.lang.RuntimeException：无法启动活动 ComponentInfo {sterlingtechsolutionpk.buttonbutton / sterlingtechsolutionpk.buttonbutton.Welcome_Screen}： java.lang.NullPointerException：尝试调用虚拟方法'void android.widget.VideoView.setVideoURI（android.net.Uri）'上为null 对象引用

.xml文件是

<android.support.constraint.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:id="@+id/frameLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/loading_screen"
android:minHeight="177dp"
tools:context="sterlingtechsolutionpk.buttonbutton.Welcome_Screen">

<!-- The primary full-screen view. This can be replaced with whatever view
     is needed to present your content, e.g. VideoView, SurfaceView,
     TextureView, etc. -->

<!-- This FrameLayout insets its children based on system windows using
     android:fitsSystemWindows. -->

<ProgressBar
    android:id="@+id/start_progres"
    style="@android:style/Widget.ProgressBar.Horizontal"
    android:layout_width="240dp"
    android:layout_height="30dp"

    android:layout_marginBottom="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="362dp"
    android:indeterminate="false"
    android:progressBackgroundTint="#fff200"
    android:progressTint="#005cef"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.455" />
<VideoView
    android:id="@+id/startingvideo"
    android:layout_width="0dp"
    android:layout_height="0dp"
    android:layout_margin="8dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintDimensionRatio="4:3"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"/>

感谢您提供有关此问题的帮助。

Answer 1

也许您使用的是错误的id？

代码：

mVideoView = findViewById(R.id.videoview);

布局：

android:id="@+id/startingvideo"

您应该更改这些行之一，以便它们匹配。

Answer 2

您为mVideoView使用了错误的ID。它返回NullPointerException，因为mVideoView是null，就像您输入错误的id一样。更改为：

mVideoView = (VideoView) findViewById(R.id.startingvideo);
尝试从initializePlayer()而不是onCreate()调用onStart();
检查videoUri是否不是null。您的getMedia方法可能返回一个null值。

VideoPlayer小部件不断提供NullPointerException，以对空对象引用调用虚拟方法

2 个答案: