在登录后的应用程序中，我必须将用户名和图像保存在其他页面的共享首选项中。我可以优先保存名称，但不知道如何保存图像。
我正在尝试类似的东西-
SharedPreferences myPrefrence;
String namePreferance="name";
String imagePreferance="image";
SharedPreferences.Editor editor = myPrefrence.edit();
editor.putString("namePreferance", itemNAme);
editor.putString("imagePreferance", itemImagePreferance);
editor.commit();
我试图将图像转换为对象后将其保存为字符串。但是当我将它重新转换为位图时，我什么也没得到。
我解决了你的问题做这样的事情：
编写方法将您的位图编码为字符串 base64-
// method for bitmap to base64
public static String encodeTobase64(Bitmap image) {
Bitmap immage = image;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
immage.compress(Bitmap.CompressFormat.PNG, 100, baos);
byte[] b = baos.toByteArray();
String imageEncoded = Base64.encodeToString(b, Base64.DEFAULT);
Log.d("Image Log:", imageEncoded);
return imageEncoded;
}
在此方法中传递您的位图，就像您喜欢的一样：
SharedPreferences.Editor editor = myPrefrence.edit();
editor.putString("namePreferance", itemNAme);
editor.putString("imagePreferance", encodeTobase64(yourbitmap));
editor.commit();
当您想在任何地方显示图像时，请使用 decode 方法再次将其转换为位图：
// method for base64 to bitmap
public static Bitmap decodeBase64(String input) {
byte[] decodedByte = Base64.decode(input, 0);
return BitmapFactory
.decodeByteArray(decodedByte, 0, decodedByte.length);
}
请在此方法中传递您的字符串并执行您想要的操作。
Finally I solved this problem.
步骤：- 1. 我在 onCreate() 中编写了一些代码，用于从之前的 Activity 中获取意图数据
private Bitmap bitmap;
Intent intent = getIntent();
if (getIntent().getExtras() != null)
{
// for get data from intent
bitmap = intent.getParcelableExtra("PRODUCT_PHOTO");
// for set this picture to imageview
your_imageView.setImageBitmap(bitmap);
sharedPreferences();
}else
{
retrivesharedPreferences();
}
2 创建 sharedPreferences() 并把这段代码
private void sharedPreferences()
{
SharedPreferences shared = getSharedPreferences("App_settings", MODE_PRIVATE);
SharedPreferences.Editor editor = shared.edit();
editor.putString("PRODUCT_PHOTO", encodeTobase64(bitmap));
editor.commit();
}
3创建retrivesharedPreferences()这个方法并放上这段代码，
private void retrivesharedPreferences()
{
SharedPreferences shared = getSharedPreferences("MyApp_Settings", MODE_PRIVATE);
String photo = shared.getString("PRODUCT_PHOTO", "photo");
assert photo != null;
if(!photo.equals("photo"))
{
byte[] b = Base64.decode(photo, Base64.DEFAULT);
InputStream is = new ByteArrayInputStream(b);
bitmap = BitmapFactory.decodeStream(is);
your_imageview.setImageBitmap(bitmap);
}
}
4 编写 encodeTobase64() 方法将您的位图编码为字符串 base64- 并将代码放入此方法中
public static String encodeTobase64(Bitmap image) {
Bitmap bitmap_image = image;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bitmap_image.compress(Bitmap.CompressFormat.PNG, 100, baos);
byte[] b = baos.toByteArray();
String imageEncoded = Base64.encodeToString(b, Base64.DEFAULT);
return imageEncoded;
}
我希望它对你有帮助。
编码为 Base64？！那是疯话！您存储到共享首选项中的信息太多了。您应该采取的策略是保存图像 URI 文件路径，然后按原样检索它。这样，您的应用程序就不会在解码图像时存储太多信息并成为内存占用者。
我在Github上做了一个简单的 App来演示这个想法，如果你想遵循：
private ImageView mImage;
private Uri mImageUri;
public void imageSelect() {
Intent intent;
if (Build.VERSION.SDK_INT < 19) {
intent = new Intent(Intent.ACTION_GET_CONTENT);
} else {
intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
intent.addCategory(Intent.CATEGORY_OPENABLE);
}
intent.setType("image/*");
startActivityForResult(Intent.createChooser(intent, "Select Picture"),
PICK_IMAGE_REQUEST);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// Check which request we're responding to
if (requestCode == PICK_IMAGE_REQUEST) {
// Make sure the request was successful
if (resultCode == RESULT_OK) {
// The user picked a image.
// The Intent's data Uri identifies which item was selected.
if (data != null) {
// This is the key line item, URI specifies the name of the data
mImageUri = data.getData();
// Removes Uri Permission so that when you restart the device, it will be allowed to reload.
this.grantUriPermission(this.getPackageName(), mImageUri, Intent.FLAG_GRANT_READ_URI_PERMISSION);
final int takeFlags = Intent.FLAG_GRANT_READ_URI_PERMISSION;
this.getContentResolver().takePersistableUriPermission(mImageUri, takeFlags);
// Saves image URI as string to Default Shared Preferences
SharedPreferences preferences =
PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("image", String.valueOf(mImageUri));
editor.commit();
// Sets the ImageView with the Image URI
mImage.setImageURI(mImageUri);
mImage.invalidate();
}
}
}
}
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
String mImageUri = preferences.getString("image", null);
mImage.setImageURI(Uri.parse(mImageUri));
就是这样！现在我们已经干净地将图像 uri 路径保存到共享首选项，并且没有浪费宝贵的系统资源对图像进行编码并将其保存到 SharedPreferences。
//Thanks Maish srivastava
// i will do complete code just copy past and run it sure worked it
//
public class MainActivity extends Activity implements OnClickListener
{
private static int RESULT_LOAD_IMAGE = 1;
public static final String MyPREFERENCES = "MyPre" ;//file name
public static final String key = "nameKey";
SharedPreferences sharedpreferences ;
Bitmap btmap;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
sharedpreferences = getSharedPreferences(MyPREFERENCES, Context.MODE_PRIVATE);
if (sharedpreferences.contains(key))
{
String u=sharedpreferences.getString(key, "");
btmap=decodeBase64(u);
ImageView iv = (ImageView) findViewById(R.id.imageView1);
iv.setImageBitmap(btmap);
}
ImageButton imgbtn=(ImageButton) findViewById(R.id.imageButton1);
imgbtn.setOnClickListener(this);
}
public void onClick(View v)
{
// TODO Auto-generated method stub
switch (v.getId())
{
case R.id.imageButton1:
try
{ //go to image library and pick the image
Intent i=newIntent(ntent.ACTION_PICK,
android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(i, RESULT_LOAD_IMAGE);
}
catch (Exception e)
{
e.printStackTrace();
}
break;
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == RESULT_LOAD_IMAGE && resultCode == RESULT_OK && null != data)
{
Uri selectedImage = data.getData();
String[] filePathColumn = { MediaStore.Images.Media.DATA };
Cursor cursor = getContentResolver().query(selectedImage, filePathColumn, null, null, null);
cursor.moveToFirst();
int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
String picturePath = cursor.getString(columnIndex);
cursor.close();
ImageView iv = (ImageView) findViewById(R.id.imageView1);
iv.setImageBitmap(BitmapFactory.decodeFile(picturePath));
btmap=BitmapFactory.decodeFile(picturePath);//decode method called
Editor editor = sharedpreferences.edit();
editor.putString(key, encodeTobase64(btmap));
editor.commit();
}
}
public static String encodeTobase64(Bitmap image)
{
Bitmap immage = image;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
immage.compress(Bitmap.CompressFormat.PNG, 100, baos);
byte[] b = baos.toByteArray();
String imageEncoded = Base64.encodeToString(b, Base64.DEFAULT);
Log.d("Image Log:", imageEncoded);
return imageEncoded;
}
public static Bitmap decodeBase64(String input)
{
byte[] decodedByte = Base64.decode(input, 0);
return BitmapFactory
.decodeByteArray(decodedByte, 0, decodedByte.length);
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}