android - 如何从 Android 的文件对话框中获取所选文件的扩展名？

Question

我正在开发一个 Android 应用程序。在我的应用程序中，我正在使用文件对话框。但我的问题是，我想检索文件对话框中所选文件的文件扩展名。

这是我的 Activity 的文件对话框关闭回调

@Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == 1 && resultCode == RESULT_OK && data != null && data.getData() != null) {
            Uri filePath = data.getData();
            try {
                //Getting the Bitmap from Gallery
                bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), filePath);
                //Setting the Bitmap to ImageView
                ivPreviewImage.setImageBitmap(bitmap);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

如何只获取文件扩展名？

更新

这是 logcat 中的错误。我在 CommonHelper 中声明了你的函数。 CommonHelper 的错误行号是你函数的返回行。

03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime: FATAL EXCEPTION: main
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime: java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { dat=content://media/external/images/media/73 }} to activity {com.blog.waiyanhein.mmfashion.mmfashion/com.blog.waiyanhein.mmfashion.mmfashion.CreateItemActivity}: java.lang.StringIndexOutOfBoundsException: length=25; index=-1
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.ActivityThread.deliverResults(ActivityThread.java:3319)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.ActivityThread.handleSendResult(ActivityThread.java:3362)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.ActivityThread.access$1100(ActivityThread.java:141)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1282)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5041)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:  Caused by: java.lang.StringIndexOutOfBoundsException: length=25; index=-1
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at java.lang.String.indexAndLength(String.java:579)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at java.lang.String.substring(String.java:1438)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at com.blog.waiyanhein.mmfashion.model.CommonHelper.getExtensionFromUri(CommonHelper.java:126)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at com.blog.waiyanhein.mmfashion.mmfashion.CreateItemActivity.onActivityResult(CreateItemActivity.java:288)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.Activity.dispatchActivityResult(Activity.java:5293)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.ActivityThread.deliverResults(ActivityThread.java:3315)
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.ActivityThread.handleSendResult(ActivityThread.java:3362) 
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.ActivityThread.access$1100(ActivityThread.java:141) 
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1282) 
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99) 
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137) 
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5041) 
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method) 
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511) 
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
03-18 13:47:09.812 815-815/com.blog.waiyanhein.mmfashion.mmfashion E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method) 

Answer 1

试试这个

如果你的文件有带扩展名的文件，你可以使用这个简单的方法:

public String getExtensionFromUri(Uri fileUri) {
    String filePath = fileUri.getPath();
    try {
        return filePath.substring(filePath.lastIndexOf(".") + 1);
    }catch(Exception e){
        return "no extension";
    }
}

否则 MimeTypeMap 应该有帮助:

public String getMIMETypeFromUri(Uri fileUri) {
    try {
        ContentResolver cR = context.getContentResolver();
        MimeTypeMap mime = MimeTypeMap.getSingleton();
        return  mime.getExtensionFromMimeType(cR.getType(fileUri));
    }catch(Exception e){
        return "no mime found";
    }
}

这是它在您的代码中的样子:

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == 1 && resultCode == RESULT_OK && data != null && data.getData() != null) {
        Uri filePath = data.getData();
        Log.d(TAG,"Extension from selected file:" + getExtensionFromUri(filePath));   
        Log.d(TAG,"Extension from MIME:" + getMIMETypeFromUri(filePath));       
         try {
            //Getting the Bitmap from Gallery
            bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), filePath);
            //Setting the Bitmap to ImageView
            ivPreviewImage.setImageBitmap(bitmap);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

希望这对您有所帮助!