我正在尝试使用Android Studio中的viewPager进行幻灯片放映。我使用BitmapFactory.Options来调整图像的大小（如果图像太大），并且在清单中使用以下代码android:largeHeap="true"
android:allowBackup="true"
如果我不使用BitmapFactory.Options调整图像大小，我想指定以上代码在我的情况下不起作用。我收到错误java.lang.OutOfMemoryError。
这是适配器的代码
public class SlideShowAdapter extends PagerAdapter {
private Context context;
private LayoutInflater inflater;
private final int HEIGHT_IMGAE = 230;
private int [] images = {
R.drawable.img1,
R.drawable.img2,
R.drawable.img3
};
public SlideShowAdapter(Context context) {
this.context = context;
}
@Override
public int getCount() {
return images.length;
}
@Override
public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
return (view == object);
}
@NonNull
@Override
public Object instantiateItem(@NonNull ViewGroup container, int position) {
inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View view = inflater.inflate(R.layout.slide_show_layout, container, false);
ImageView img = view.findViewById(R.id.sile_show_layout_imageView);
DisplayMetrics displayMetrics = new DisplayMetrics();
((Activity)context).getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
int width = displayMetrics.widthPixels;
img.setImageBitmap(
decodeSampledBitmapFromResource(context.getResources(), images[position], width, HEIGHT_IMGAE));
container.addView(view);
return view;
}
@Override
public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
container.removeView((LinearLayout)object);
}
private static int calculateInSampleSize(
BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int halfHeight = height / 2;
final int halfWidth = width / 2;
// Calculate the largest inSampleSize value that is a power of 2 and keeps both
// height and width larger than the requested height and width.
while ((halfHeight / inSampleSize) >= reqHeight
&& (halfWidth / inSampleSize) >= reqWidth) {
inSampleSize *= 2;
}
}
return inSampleSize;
}
private static Bitmap decodeSampledBitmapFromResource(Resources res, int resId,
int reqWidth, int reqHeight) {
// First decode with inJustDecodeBounds=true to check dimensions
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(res, resId, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
return BitmapFactory.decodeResource(res, resId, options);
}
}
一切在main上都正常
public class MainActivity extends AppCompatActivity {
private ViewPager slideShow;
private SlideShowAdapter adapter ;
private int currentPage = 0;
Timer timer;
final long DELAY_MS = 3000; //delay in milliseconds before task is to be executed
final long PERIOD_MS = 5000; // time in milliseconds between successive task executions.
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
slideShow = findViewById(R.id.main_activity_viewPager_slideshow);
adapter = new SlideShowAdapter(this);
slideShow.setAdapter(adapter);
this.doSlideShow();
}
public void doSlideShow(){
final Handler handler = new Handler();
final Runnable Update = new Runnable() {
public void run() {
if (currentPage == adapter.getCount()) {
currentPage = 0;
}
slideShow.setCurrentItem(currentPage++, true);
}
};
timer = new Timer(); // This will create a new Thread
timer.schedule(new TimerTask() { // task to be scheduled
@Override
public void run() {
handler.post(Update);
}
}, DELAY_MS, PERIOD_MS);
}
public void luchAdminActivity(View view) {
startActivity(new Intent(this,SingupActivity.class));
}
public void luchMainActivity(View view) {
startActivity(new Intent(this,MainActivity.class));
}
public void luchMenuActivity(View view) {
startActivity(new Intent(this,MainActivity.class));
}
}
但是当我转到另一个活动并尝试返回到主活动（有幻灯片放映的地方）时，出现以下错误
Process: bogdan.yourwaiter, PID: 25647
java.lang.OutOfMemoryError: Failed to allocate a 156487692 byte allocation with 16768376 free bytes and 114MB until OOM
at dalvik.system.VMRuntime.newNonMovableArray(Native Method)
at android.graphics.BitmapFactory.nativeDecodeAsset(Native Method)
at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:700)
at android.graphics.BitmapFactory.decodeResourceStream(BitmapFactory.java:535)
at android.graphics.BitmapFactory.decodeResource(BitmapFactory.java:558)
at bogdan.yourwaiter.adapter.SlideShowAdapter.decodeSampledBitmapFromResource(SlideShowAdapter.java:111)
at bogdan.yourwaiter.adapter.SlideShowAdapter.instantiateItem(SlideShowAdapter.java:61)
at androidx.viewpager.widget.ViewPager.addNewItem(ViewPager.java:1010)
at androidx.viewpager.widget.ViewPager.populate(ViewPager.java:1224)
at androidx.viewpager.widget.ViewPager.populate(ViewPager.java:1092)
at androidx.viewpager.widget.ViewPager.onMeasure(ViewPager.java:1622)
at android.view.View.measure(View.java:21121)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6462)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)
at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1117)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:642)
at android.view.View.measure(View.java:21121)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:715)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)
at android.view.View.measure(View.java:21121)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6462)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at androidx.appcompat.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:143)
at android.view.View.measure(View.java:21121)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6462)
at androidx.appcompat.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:401)
at android.view.View.measure(View.java:21121)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6462)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at android.view.View.measure(View.java:21121)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6462)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:758)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:640)
at android.view.View.measure(View.java:21121)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6462)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at com.android.internal.policy.DecorView.onMeasure(DecorView.java:872)
at android.view.View.measure(View.java:21121)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2625)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1677)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1928)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1550)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7190)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:959)
at android.view.Choreographer.doCallbacks(Choreographer.java:734)
at android.view.Choreographer.doFrame(Choreographer.java:670)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:945)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6776)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1496)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1386)