You must add following code for taking images from devices
choosebtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i1=new Intent();
i1.setType("image/*");
i1.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(i1,1);
}
});
@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if(requestCode == 1 && resultCode == RESULT_OK && data != null && data.getData() != null)
{
imguri=data.getData();
mainpreview.setImageURI(data.getData());
} else {
Toast.makeText(getApplicationContext(),"please choose image",Toast.LENGTH_SHORT).show();
}
}