JAVAlang.NullPointerException:com上的uri。安卓内部的util。先决条件。checkNotNull

Question

我在查询提交表单中使用多部分上传进行图像上传，在我的情况下，图像上传是可选的，所以当我不使用图像时，它会抛出空指针，所以我需要它是可选的

 public String getPath(Uri uri) {
        Cursor cursor = AskQueryActivity.this.getContentResolver().query(uri, null, null, null, null); // this line throws error
        assert cursor != null;
        cursor.moveToFirst();
        String document_id = cursor.getString(0);
        document_id = document_id.substring(document_id.lastIndexOf(":") + 1);
        cursor.close();

        cursor = AskQueryActivity.this.getContentResolver().query(
                安卓.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
                null, MediaStore.Images.Media._ID + " = ? ", new String[]{document_id}, null);
        assert cursor != null;
        cursor.moveToFirst();
        String path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
        cursor.close();

        return path;
    }

错误日志

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.admin.lorem.ipsum, PID: 3818
                  java.lang.NullPointerException: uri
                      at com.安卓.internal.util.Preconditions.checkNotNull(Preconditions.java:60)
                      at 安卓.content.ContentResolver.query(ContentResolver.java:474)
                      at 安卓.content.ContentResolver.query(ContentResolver.java:434)

Answer 1

由于@albert_nil state here检查URI不应为空以执行Cursor query，如果URI仍然返回null，则通过Toast or log如下方式处理

 public String getPath(Uri uri) {
  if(uri != null){
    Cursor cursor = AskQueryActivity.this.getContentResolver().query(uri, null, null, null, null); // this line throws error
    assert cursor != null;
    cursor.moveToFirst();
    String document_id = cursor.getString(0);
    document_id = document_id.substring(document_id.lastIndexOf(":") + 1);
    cursor.close();

    cursor = AskQueryActivity.this.getContentResolver().query(
            android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
            null, MediaStore.Images.Media._ID + " = ? ", new String[]{document_id}, null);
    assert cursor != null;
    cursor.moveToFirst();
    String path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
    cursor.close();

    return path;
  } else{
     //do log/toast to user
     return "";
  }
}

Answer 2

Intent intentt = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
intentt.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION & Intent.FLAG_GRANT_WRITE_URI_PERMISSION);

只需将此添加到intent或ActivityResult中即可

protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
    if(resultCode != RESULT_CANCELED){
        if (requestCode == CAMERA_REQUEST) {  
            Bitmap photo = (Bitmap) data.getExtras().get("data"); 
            imageView.setImageBitmap(photo);
        }
    }
}