用Intent隐式跳转调用相册回调

package com.work.list.jiwazii;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.support.annotation.Nullable;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.RadioGroup;
import android.widget.Toast;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
private Button button;

private final int RC_CAMERA = 1;
private final int RC_ALBUM = 2;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //通过intent隐式跳转获取系统相机相册
    //初始化控件
    initView();
    //点击事件
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //点击按钮触发事件
            openbutton();
        }
    });
}

private void openbutton() {
    //定义dialog
    AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
    builder.setTitle("请选择");
    builder.setItems(new String[]{"相机", "相册"}, new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            switch (which) {
                //相机
                case 0:
                    Intent intent_camera = new Intent("android.media.action.IMAGE_CAPTURE");
                    startActivityForResult(intent_camera, RC_CAMERA);//rc_camera
                    break;
                //相册
                case 1:
                    Intent intent_album = new Intent(Intent.ACTION_PICK);
                    intent_album.setType("image/*");
                    startActivityForResult(intent_album,RC_ALBUM);
                    break;
            }
        }
    });
    builder.create().show();
}

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    switch (requestCode) {
        case RC_CAMERA:
            Toast.makeText(MainActivity.this, "相机回调", Toast.LENGTH_SHORT).show();
            break;
        case RC_ALBUM:
            Toast.makeText(MainActivity.this, "相册回调", Toast.LENGTH_SHORT).show();
            break;
    }
}

private void initView() {
    button = findViewById(R.id.button);
}

}
//----------------布局----------------

<?xml version="1.0" encoding="utf-8"?>

<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="选择图片"
    android:textSize="25sp" />