在 Android 中从内存中保存和读取位图/图像

小开

最佳答案

使用下面的代码将图像保存到内部目录。

private String saveToInternalStorage(Bitmap bitmapImage){
ContextWrapper cw = new ContextWrapper(getApplicationContext());
// path to /data/data/yourapp/app_data/imageDir
File directory = cw.getDir("imageDir", Context.MODE_PRIVATE);
// Create imageDir
File mypath=new File(directory,"profile.jpg");


FileOutputStream fos = null;
try {
fos = new FileOutputStream(mypath);
// Use the compress method on the BitMap object to write image to the OutputStream
bitmapImage.compress(Bitmap.CompressFormat.PNG, 100, fos);
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return directory.getAbsolutePath();
}

说明:

1.将使用给定的名称创建目录。Javadocs 用于告诉它将在何处确切地创建目录。

2. 必须给出保存图像所使用的图像名称。

从内存读取文件。使用以下代码

private void loadImageFromStorage(String path)
{


try {
File f=new File(path, "profile.jpg");
Bitmap b = BitmapFactory.decodeStream(new FileInputStream(f));
ImageView img=(ImageView)findViewById(R.id.imgPicker);
img.setImageBitmap(b);
}
catch (FileNotFoundException e)
{
e.printStackTrace();
}


}

小开

今天碰到这个问题，我就是这么做的。只需使用所需的参数

调用这个函数

public void saveImage(Context context, Bitmap bitmap, String name, String extension){
name = name + "." + extension;
FileOutputStream fileOutputStream;
try {
fileOutputStream = context.openFileOutput(name, Context.MODE_PRIVATE);
bitmap.compress(Bitmap.CompressFormat.JPEG, 90, fileOutputStream);
fileOutputStream.close();
} catch (Exception e) {
e.printStackTrace();
}
}

类似地，要读取相同的内容，请使用

public Bitmap loadImageBitmap(Context context,String name,String extension){
name = name + "." + extension
FileInputStream fileInputStream
Bitmap bitmap = null;
try{
fileInputStream = context.openFileInput(name);
bitmap = BitmapFactory.decodeStream(fileInputStream);
fileInputStream.close();
} catch(Exception e) {
e.printStackTrace();
}
return bitmap;
}

小开

/**
* Created by Ilya Gazman on 3/6/2016.
*/
public class ImageSaver {


private String directoryName = "images";
private String fileName = "image.png";
private Context context;
private boolean external;


public ImageSaver(Context context) {
this.context = context;
}


public ImageSaver setFileName(String fileName) {
this.fileName = fileName;
return this;
}


public ImageSaver setExternal(boolean external) {
this.external = external;
return this;
}


public ImageSaver setDirectoryName(String directoryName) {
this.directoryName = directoryName;
return this;
}


public void save(Bitmap bitmapImage) {
FileOutputStream fileOutputStream = null;
try {
fileOutputStream = new FileOutputStream(createFile());
bitmapImage.compress(Bitmap.CompressFormat.PNG, 100, fileOutputStream);
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (fileOutputStream != null) {
fileOutputStream.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}


@NonNull
private File createFile() {
File directory;
if(external){
directory = getAlbumStorageDir(directoryName);
}
else {
directory = context.getDir(directoryName, Context.MODE_PRIVATE);
}
if(!directory.exists() && !directory.mkdirs()){
Log.e("ImageSaver","Error creating directory " + directory);
}


return new File(directory, fileName);
}


private File getAlbumStorageDir(String albumName) {
return new File(Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_PICTURES), albumName);
}


public static boolean isExternalStorageWritable() {
String state = Environment.getExternalStorageState();
return Environment.MEDIA_MOUNTED.equals(state);
}


public static boolean isExternalStorageReadable() {
String state = Environment.getExternalStorageState();
return Environment.MEDIA_MOUNTED.equals(state) ||
Environment.MEDIA_MOUNTED_READ_ONLY.equals(state);
}


public Bitmap load() {
FileInputStream inputStream = null;
try {
inputStream = new FileInputStream(createFile());
return BitmapFactory.decodeStream(inputStream);
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (inputStream != null) {
inputStream.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
}

用法

储存:

new ImageSaver(context).
setFileName("myImage.png").
setDirectoryName("images").
save(bitmap);

To load:

Bitmap bitmap = new ImageSaver(context).
setFileName("myImage.png").
setDirectoryName("images").
load();

Edit:

Added ImageSaver.setExternal(boolean) to support saving to external storage based on googles example.

小开

对于 Kotlin 用户，我创建了一个 ImageStorageManager类，它可以轻松地处理图像的保存、获取和删除操作:

class ImageStorageManager {
companion object {
fun saveToInternalStorage(context: Context, bitmapImage: Bitmap, imageFileName: String): String {
context.openFileOutput(imageFileName, Context.MODE_PRIVATE).use { fos ->
bitmapImage.compress(Bitmap.CompressFormat.PNG, 25, fos)
}
return context.filesDir.absolutePath
}


fun getImageFromInternalStorage(context: Context, imageFileName: String): Bitmap? {
val directory = context.filesDir
val file = File(directory, imageFileName)
return BitmapFactory.decodeStream(FileInputStream(file))
}


fun deleteImageFromInternalStorage(context: Context, imageFileName: String): Boolean {
val dir = context.filesDir
val file = File(dir, imageFileName)
return file.delete()
}
}
}

阅读更多给你

小开

//多重图像检索

 File folPath = new File(getIntent().getStringExtra("folder_path"));
File[] imagep = folPath.listFiles();


for (int i = 0; i < imagep.length ; i++) {
imageModelList.add(new ImageModel(imagep[i].getAbsolutePath(), Uri.parse(imagep[i].getAbsolutePath())));
}
imagesAdapter.notifyDataSetChanged();

小开

如果你想按照 Android 10的实践在存储器中编写代码，请点击这里如果你只想图像是应用程序特定的，给你例如，如果你想存储一个图像只是为了你的应用程序使用:

viewModelScope.launch(Dispatchers.IO) {
getApplication<Application>().openFileOutput(filename, Context.MODE_PRIVATE).use {
bitmap.compress(Bitmap.CompressFormat.PNG, 50, it)
}
}

GetApplication 是一种为 ViewModel 提供上下文的方法，它是 AndroidViewModel 的一部分稍后，如果你想阅读它:

viewModelScope.launch(Dispatchers.IO) {
val savedBitmap = BitmapFactory.decodeStream(
getApplication<App>().openFileInput(filename).readBytes().inputStream()
)
}

小开

确保使用 WEBP 作为媒体格式，以同样的质量节省更多的空间:

fun saveImage(context: Context, bitmap: Bitmap, name: String): String {
context.openFileOutput(name, Context.MODE_PRIVATE).use { fos ->
bitmap.compress(Bitmap.CompressFormat.WEBP, 25, fos)
}
return context.filesDir.absolutePath
}

小开

此代码将支持 UptoAndroid11 + 。

< strong > 在片段/活动上声明一个权限结果我正在使用一个片段

private val askPermissions =
registerForActivityResult(ActivityResultContracts.RequestMultiplePermissions()) { permissions ->
val isGranted = permissions.entries.all {
it.value == true
}


if (isGranted) {
viewModel.saveImageToGallery(requireContext().contentResolver,
getString(R.string.my_deshi_qr_code),
bitmap)
} else {
askForWritePermission()
}
}

触发事件

bindingView.downloadQrButton.setOnClickListener {
requestPermission()
}
private fun requestPermission() {
val minSDK = Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q
val isWritePermissionGranted = (ContextCompat.checkSelfPermission(requireContext(),
Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) || minSDK


if (!isWritePermissionGranted) {
askForWritePermission()
} else {
viewModel.saveImageToGallery(requireContext().contentResolver,
getString(R.string.my_deshi_qr_code),
bitmap)
}
}




private fun askForWritePermission() {
askPermissions.launch(listOf(Manifest.permission.WRITE_EXTERNAL_STORAGE).toTypedArray())
}

视图模型

fun saveImageToGallery(contentResolver: ContentResolver, imageName: String, bitmap: Bitmap?) {
val imageUri: Uri?
val contentValues = ContentValues().apply {
put(MediaStore.MediaColumns.DISPLAY_NAME, "$imageName.jpg")
put(MediaStore.MediaColumns.MIME_TYPE, "image/jpeg")
bitmap?.let {
put(MediaStore.Images.Media.WIDTH, bitmap.width)
put(MediaStore.Images.Media.HEIGHT, bitmap.height)
}
}


imageUri = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
contentValues.put(MediaStore.MediaColumns.RELATIVE_PATH,
Environment.DIRECTORY_PICTURES + File.separator.toString() + "YourFolderName")
MediaStore.Images.Media.getContentUri(MediaStore.VOLUME_EXTERNAL_PRIMARY)
} else {
MediaStore.Images.Media.EXTERNAL_CONTENT_URI
}


try {
val uri = contentResolver.insert(imageUri, contentValues)
val fos = uri?.let { contentResolver.openOutputStream(it) }
bitmap?.compress(Bitmap.CompressFormat.JPEG, 100, fos)
Objects.requireNonNull(fos)
_showMessage.postValue(Event("Image Saved"))
} catch (e: Exception) {
_showMessage.postValue(Event("Image Not Saved \n$e"))
}
}