在棒棒糖 (5.1.1) 中加载 JPEG 图像

Question

我想在Android应用程序上加载JPEG图像作为位图对象。我使用的是安卓 5.1.1 API 22。我目前正在使用以下代码加载位图，其中jpg是我之前拍摄的图像的文件：

File root = Environment.getExternalStorageDirectory();
BitmapFactory.Options bmOptions = new BitmapFactory.Options();
bmOptions.inJustDecodeBounds = false;
bmOptions.inSampleSize = 1;
Bitmap bMap = BitmapFactory.decodeFile(jpg.getAbsolutePath(),bmOptions);

我正在尝试对上面提取的位图执行图像处理：

int width = bMap.getWidth();
int height = bMap.getHeight();

我在清单文件中设置了以下权限：

<uses-permission
android:name="android.permission.WRITE_EXTERNAL_STORAGE"
android:maxSdkVersion="18" />

在日志中，我得到以下输出：

java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:389)
at android.view.View.performClick(View.java:5254)
at android.view.View$PerformClick.run(View.java:21173)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6838)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:384)
at android.view.View.performClick(View.java:5254) 
at android.view.View$PerformClick.run(View.java:21173) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:145) 
at android.app.ActivityThread.main(ActivityThread.java:6838) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.graphics.Bitmap.getWidth()' on a null object reference

所以本质上它是说位图是空的(logcat的最后一行(。

有没有其他人在安卓 5.1.1 上遇到过这个问题;API 22？还是有人有不同的方法？任何帮助将不胜感激！谢谢:)

Answer 1

如果要从库中选择位图图像，则可能获得的路径不正确。 添加一个名为 file_paths.xml 的新 XML 文件

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
<external-path name="my_images"
path="." />
</paths>

在 Android Manifest 中添加此内部标记

<provider
android:name="android.support.v4.content.FileProvider"
android:authorities="${applicationId}.provider"
android:exported="false"
android:grantUriPermissions="true">
<meta-data
android:name="android.support.FILE_PROVIDER_PATHS"
android:resource="@xml/file_paths">
</meta-data>
</provider>

在活动中：

public String getPathFromURI(Uri contentUri) {
try {
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
String res = "";
String[] proj = {MediaStore.Images.Media.DATA};
Cursor cursor = getActivity().getContentResolver().query(contentUri, proj, null, null, null);
if (cursor.moveToFirst()) {
int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
res = cursor.getString(column_index);
}
cursor.close();
return res;
} else {
String res = "";
String wholeID = null;
wholeID = DocumentsContract.getDocumentId(contentUri);
String id = wholeID.split(":")[1];
String[] column = {MediaStore.Images.Media.DATA};
String sel = MediaStore.Images.Media._ID + "=?";
Cursor cursor = getActivity().getContentResolver().
query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
column, sel, new String[]{id}, null);
int columnIndex = cursor.getColumnIndex(column[0]);
if (cursor.moveToFirst()) {
res = cursor.getString(columnIndex);
}
cursor.close();
return res;
}
} catch (Exception e) {
Cursor cursor = null;
try {
String[] proj = {MediaStore.Images.Media.DATA};
cursor = getContext().getContentResolver().query(contentUri, proj, null, null, null);
int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
cursor.moveToFirst();
return cursor.getString(column_index);
} catch (Exception ex) {
return null;
} finally {
if (cursor != null) {
cursor.close();
}
}
}
}