调用系统的camera

package com.qiaoguo.camara;

import android.content.Intent;
import android.content.IntentFilter;
import android.net.Uri;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

import java.io.File;

public class MainActivity extends AppCompatActivity {

    public static final String PATHNAME = Environment.getExternalStorageDirectory() + "/meipaipai" + "/dd.jpg";
    public static final int REQUEST_CODE = 0;
    private Button pai;
    private ImageView img;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        Intent intent=new Intent();
        intent.setAction(MediaStore.ACTION_IMAGE_CAPTURE);
        intent.addCategory(Intent.CATEGORY_DEFAULT);
        File file=new File(PATHNAME);
        if (file.exists()){
            file.delete();
        }
        Uri uri=Uri.fromFile(file);
        intent.putExtra(MediaStore.EXTRA_OUTPUT,uri);
        startActivity(intent);
        startActivityForResult(intent, REQUEST_CODE);

        pai.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });

    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode==REQUEST_CODE){
            File file=new File(PATHNAME);
            if(file.exists()){
               img.setImageURI(Uri.fromFile(file));
            }
        }
    }

    private void initView() {
        pai = (Button) findViewById(R.id.btn_pai);
        img = (ImageView) findViewById(R.id.img);
    }
}