1.代码如下

import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.v4.content.FileProvider;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.InputStream;

import butterknife.BindView;
import butterknife.ButterKnife;


public class MainActivity extends AppCompatActivity {

    private static final int TAKE_PHOTO = 1000;
    private static final int CHOOSE_PHOTO = 2000;
    private static final int CROP_PHOTO = 3000;
    private String imagePath;
    private Uri imageUri;

    @BindView(R.id.take_photo_button)
    Button take_photo_button;
    @BindView(R.id.choose_from_album_button)
    Button choose_from_album_button;
    @BindView(R.id.picture_imageView )
    ImageView picture_imageView ;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);
        imagePath = getExternalCacheDir() + "/image.jpg"; // 设置文件保存的路径
        initView();
    }


    private void initView() {
        take_photo_button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                imageUri = file2Uri(imagePath);
                takePhoto(imageUri);
            }
        });


        choose_from_album_button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                openAlbum();
            }
        });
    }


    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode != RESULT_OK) {
            return;
        }

        switch (requestCode) {
            case TAKE_PHOTO:
                // 裁剪拍摄的照片
                imageUri = cropPhoto(imageUri);
                break;

            case CHOOSE_PHOTO:
                // 裁剪从相册选择的照片
                Uri uri = data.getData();
                imageUri = cropPhoto(uri);
                break;

            case CROP_PHOTO:
                // 显示图片
                BitmapFactory.Options options = new BitmapFactory.Options();
                options.inJustDecodeBounds = false; // false表示返回Bitmap;true表示返回null,获取图片信息的时候用
                options.inSampleSize = 2; // 设置图片宽高为原图的1/2
                Bitmap bitmap = null;
                try {
                    InputStream ins = getContentResolver().openInputStream(imageUri);
                    bitmap = BitmapFactory.decodeStream(ins, null, options);
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                }
                /*Cursor cursor = getContentResolver().query(imageUri, null, null, null, null);
                if (null != cursor) {
                    if (cursor.moveToFirst()) {
                        imagePath = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
                    }
                }*/
                // bitmap = BitmapFactory.decodeFile(imagePath, options);
                picture_imageView.setImageBitmap(bitmap);
                break;

            default:
                break;
        }
    }


    /**
     * 创建图片的File对象并转化成Uri返回
     * @return
     */
    private Uri file2Uri(String imagePath) {
        Uri uri = null;
        File file = new File(imagePath);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            uri = FileProvider.getUriForFile(MainActivity.this, "cn.com.pirate.demo.fileprovier", file);
        } else {
            uri = Uri.fromFile(file);
        }
        return uri;
    }


    /**
     * 启动相机
     * @param uri
     */
    private void takePhoto(Uri uri) {
        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        intent.putExtra(MediaStore.EXTRA_OUTPUT, uri);
        startActivityForResult(intent, TAKE_PHOTO);
    }


    /**
     * 打开相册
     */
    private void openAlbum() {
        Intent intent = new Intent(Intent.ACTION_PICK);
        // Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.setType("image/*");
        startActivityForResult(intent, CHOOSE_PHOTO);
    }


    /**
     * 裁切图片并返回Uri
     * @param uri
     */
    private Uri cropPhoto(Uri uri) {
        Uri imageUri = Uri.fromFile(new File(imagePath));
        Intent intent = new Intent("com.android.camera.action.CROP");
        // 赋予权限,否则7.0以上版本无法裁切图片
        intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        intent.addFlags(Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
        intent.setDataAndType(uri, "image/*");
        intent.putExtra("crop", "true");
        intent.putExtra("scale", true);
        // aspectX,aspectY是宽高的比例  
        intent.putExtra("aspectX", 1);
        intent.putExtra("aspectY", 1);
        // outputX,outputY是裁剪图片宽高  
        // intent.putExtra("outputX", 800);
        // intent.putExtra("outputY", 800);
        intent.putExtra("return-data", false);
        intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
        startActivityForResult(intent, CROP_PHOTO);
        return imageUri;
    }
}

2.在AndroidManifest.xml中添加

<provider
    android:authorities="cn.com.pirate.demo.fileprovier"
    android:name="android.support.v4.content.FileProvider"
    android:grantUriPermissions="true">
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/file_path"/>
</provider>

3.在res文件加下添加xml/file_path.xml文件，内容如下

<?xml version="1.0" encoding="utf-8"?>
<paths>
    <external-path name = "share" path = "" />
</paths>

4.对应的布局文件为layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="cn.com.pirate.demo.MainActivity">

    <Button
        android:id="@+id/take_photo_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="50dp"
        android:layout_marginRight="50dp"
        android:layout_marginTop="10dp"
        android:layout_marginBottom="5dp"
        android:textAllCaps="false"
        android:text="take_photo"/>

    <Button
        android:id="@+id/choose_from_album_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="50dp"
        android:layout_marginRight="50dp"
        android:layout_marginTop="5dp"
        android:layout_marginBottom="5dp"
        android:textAllCaps="false"
        android:text="choose_from_album"/>

    <ImageView
        android:id="@+id/picture_imageView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="center_horizontal"/>

</LinearLayout>