调取系统的相机（展示图片）

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

import java.io.File;

public class MainActivity extends AppCompatActivity {

    private Button btn_StartCamera, btn_StartCameraInGallery;
    private ImageView iv_CameraImg;

    private static final String TAG = "main";
    private static final String FILE_PATH = "/sdcard/syscamera.jpg";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
                 btn_StartCamera = (Button) findViewById(R.id.btn_StartCamera);
                 btn_StartCameraInGallery = (Button) findViewById(R.id.btn_StartCameraInGallery);
                 iv_CameraImg = (ImageView) findViewById(R.id.iv_CameraImg);

                 btn_StartCamera.setOnClickListener(click);
                 btn_StartCameraInGallery.setOnClickListener(click);
    }
    private View.OnClickListener click = new View.OnClickListener() {

                 @Override
         public void onClick(View v) {

                         Intent intent = null;
                         switch (v.getId()) {
                             // 指定相机拍摄照片保存地址
                             case R.id.btn_StartCamera:
                                     intent = new Intent();
                                     // 指定开启系统相机的Action
                                     intent.setAction(MediaStore.ACTION_IMAGE_CAPTURE);
                                     intent.addCategory(Intent.CATEGORY_DEFAULT);
                                     // 根据文件地址创建文件
                                     File file = new File(FILE_PATH);
                                     if (file.exists()) {
                                         file.delete();
                                         }
                                     // 把文件地址转换成Uri格式
                                     Uri uri = Uri.fromFile(file);
                                     // 设置系统相机拍摄照片完成后图片文件的存放地址
                                     intent.putExtra(MediaStore.EXTRA_OUTPUT, uri);
                                     startActivityForResult(intent, 0);
                                     break;
                             // 不指定相机拍摄照片保存地址
                             case R.id.btn_StartCameraInGallery:
                                     intent = new Intent();
                                     // 指定开启系统相机的Action
                                     intent.setAction(MediaStore.ACTION_IMAGE_CAPTURE);
                                     intent.addCategory(Intent.CATEGORY_DEFAULT);
                                     startActivityForResult(intent, 1);
                                     break;
                             default:
                                     break;
                             }

                     }
     };

             @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent data) {
                 Log.i(TAG, "系统相机拍照完成，resultCode="+resultCode);

                 if (requestCode == 0) {
                         File file = new File(FILE_PATH);
                         Uri uri = Uri.fromFile(file);
                         iv_CameraImg.setImageURI(uri);
                     } else if (requestCode == 1) {
                         Log.i(TAG, "默认content地址："+data.getData());
                         iv_CameraImg.setImageURI(data.getData());
                     }
             }
}

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:layout_editor_absoluteY="81dp">

    <android.support.constraint.Guideline
        android:id="@+id/guideline"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.18229167" />

    <Button
        android:id="@+id/btn_StartCamera"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="第一个"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.242"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.29000002" />

    <Button
        android:id="@+id/btn_StartCameraInGallery"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="@+id/btn_StartCamera"
        app:layout_constraintStart_toEndOf="@+id/btn_StartCamera"
        app:layout_constraintTop_toTopOf="@+id/btn_StartCamera" />

    <ImageView
        android:id="@+id/iv_CameraImg"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn_StartCameraInGallery"
        app:srcCompat="@mipmap/ic_launcher" />

</android.support.constraint.ConstraintLayout>