下面这些功能都需要在Activity中实现，如果在fragment中，则

//Fragment中调用activity方法
MainActivity activity=(MainActivity)getActivity();
activity.openPhotoAlbum();

主要是访问权限和数据转换

1  访问权限

    在Manifest中授权

 <uses-feature
        android:name="android.hardware.camera"
        android:required="true"
        />

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.CAMERA"/>
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"
        tools:ignore="ProtectedPermissions" />
    <uses-permission android:name="com.sichuanwww.showpic.permission.ACCESS_PROVIDER"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-feature android:name="android.hardware.camera.autofocus" />

在代码中也需要动态授权

2  基本布局

    一个ImageView   一个textView     一个button

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <ImageView
            android:id="@+id/imageView"
            android:layout_width="wrap_content"
            android:layout_height="0dp"
            android:layout_weight="4"
            tools:srcCompat="@mipmap/ic_launcher" />

        <TextView
            android:id="@+id/txt"
        android:layout_width="wrap_content"
        android:layout_height="0dp"
            android:layout_weight="4"
        android:text="Hello wwwww"      />

        <Button
            android:id="@+id/button"
            android:layout_width="wrap_content"
            android:layout_height="0dp"
            android:layout_weight="4"
            android:text="PhotoAlbum" />

</LinearLayout>

3   功能代码

package com.sichuanwww.showpic;

import android.Manifest;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    String[] mPermissionList = new String[]{
            Manifest.permission.WRITE_EXTERNAL_STORAGE,
            Manifest.permission.READ_EXTERNAL_STORAGE};
    public static final int REQUEST_PICK_IMAGE = 11101;
    private ImageView mShowImg;
    private TextView  tx;
    private Button bt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mShowImg = (ImageView) findViewById(R.id.imageView);
        tx = (TextView) findViewById(R.id.txt);
        bt=(Button) findViewById(R.id.button);

        mShowImg.setImageResource(R.mipmap.ic_launcher);
        bt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                /*
                //函数调用顺序： openPhotoAlbum              >>
                                onRequestPermissionsResult  >>
                                getImage                    >>
                                onActivityResult            >>
                */

                openPhotoAlbum();
            }
        });

    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode) {
            case 100:
                boolean writeExternalStorage = grantResults[0] == PackageManager.PERMISSION_GRANTED;
                boolean readExternalStorage = grantResults[1] == PackageManager.PERMISSION_GRANTED;

                if (grantResults.length > 0 && writeExternalStorage && readExternalStorage) {
                    getImage();
                } else {
                    Toast.makeText(this, "请设置必要权限", Toast.LENGTH_SHORT).show();
                }

                break;
        }
    }

    private void getImage() {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
            startActivityForResult(new Intent(Intent.ACTION_GET_CONTENT).setType("image/*"),
                    REQUEST_PICK_IMAGE);
        } else {
            Intent intent = new Intent(Intent.ACTION_PICK, null);
            intent.setDataAndType(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "image/*");
            startActivityForResult(intent, REQUEST_PICK_IMAGE);
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == Activity.RESULT_OK) {
            switch (requestCode) {
                case REQUEST_PICK_IMAGE:
                    if (data != null) {
                        String realPathFromUri = RealPathFromUriUtils.getRealPathFromUri(this, data.getData());
                        tx.setText(realPathFromUri);
                        mShowImg.setImageURI(data.getData());
                    } else {
                        Toast.makeText(this, "图片损坏，请重新选择", Toast.LENGTH_SHORT).show();
                    }
                    break;
            }
        }
    }
    //打开相册
    public void openPhotoAlbum() {
        ActivityCompat.requestPermissions(MainActivity.this, mPermissionList, 100);
    }



}

代码本身很简单，只是有很多坑。

4  获取图片真实路径代码

    如果只是显示，则可以不用，只是需要上传文件时使用

package com.sichuanwww.showpic;
import android.annotation.SuppressLint;
import android.content.ContentUris;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.os.Build;
import android.provider.DocumentsContract;
import android.provider.MediaStore;

public class RealPathFromUriUtils {
    /**
     * 根据Uri获取图片的绝对路径
     *
     * @param context 上下文对象
     * @param uri   图片的Uri
     * @return 如果Uri对应的图片存在, 那么返回该图片的绝对路径, 否则返回null
     */
    public static String getRealPathFromUri(Context context, Uri uri) {
        int sdkVersion = Build.VERSION.SDK_INT;
        if (sdkVersion >= 19) { // api >= 19
            return getRealPathFromUriAboveApi19(context, uri);
        } else { // api < 19
            return getRealPathFromUriBelowAPI19(context, uri);
        }
    }

    /**
     * 适配api19以下(不包括api19),根据uri获取图片的绝对路径
     *
     * @param context 上下文对象
     * @param uri   图片的Uri
     * @return 如果Uri对应的图片存在, 那么返回该图片的绝对路径, 否则返回null
     */
    private static String getRealPathFromUriBelowAPI19(Context context, Uri uri) {
        return getDataColumn(context, uri, null, null);
    }

    /**
     * 适配api19及以上,根据uri获取图片的绝对路径
     *
     * @param context 上下文对象
     * @param uri   图片的Uri
     * @return 如果Uri对应的图片存在, 那么返回该图片的绝对路径, 否则返回null
     */
    @SuppressLint("NewApi")
    private static String getRealPathFromUriAboveApi19(Context context, Uri uri) {
        String filePath = null;
        if (DocumentsContract.isDocumentUri(context, uri)) {
            // 如果是document类型的 uri, 则通过document id来进行处理
            String documentId = DocumentsContract.getDocumentId(uri);
            if (isMediaDocument(uri)) { // MediaProvider
                // 使用':'分割
                String id = documentId.split(":")[1];

                String selection = MediaStore.Images.Media._ID + "=?";
                String[] selectionArgs = {id};
                filePath = getDataColumn(context, MediaStore.Images.Media.EXTERNAL_CONTENT_URI, selection, selectionArgs);
            } else if (isDownloadsDocument(uri)) { // DownloadsProvider
                Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"), Long.valueOf(documentId));
                filePath = getDataColumn(context, contentUri, null, null);
            }
        } else if ("content".equalsIgnoreCase(uri.getScheme())) {
            // 如果是 content 类型的 Uri
            filePath = getDataColumn(context, uri, null, null);
        } else if ("file".equals(uri.getScheme())) {
            // 如果是 file 类型的 Uri,直接获取图片对应的路径
            filePath = uri.getPath();
        }
        return filePath;
    }

    /**
     * 获取数据库表中的 _data 列，即返回Uri对应的文件路径
     *
     * @return
     */
    private static String getDataColumn(Context context, Uri uri, String selection, String[] selectionArgs) {
        String path = null;

        String[] projection = new String[]{MediaStore.Images.Media.DATA};
        Cursor cursor = null;
        try {
            cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs, null);
            if (cursor != null && cursor.moveToFirst()) {
                int columnIndex = cursor.getColumnIndexOrThrow(projection[0]);
                path = cursor.getString(columnIndex);
            }
        } catch (Exception e) {
            if (cursor != null) {
                cursor.close();
            }
        }
        return path;
    }

    /**
     * @param uri the Uri to check
     * @return Whether the Uri authority is MediaProvider
     */
    private static boolean isMediaDocument(Uri uri) {
        return "com.android.providers.media.documents".equals(uri.getAuthority());
    }

    /**
     * @param uri the Uri to check
     * @return Whether the Uri authority is DownloadsProvider
     */
    private static boolean isDownloadsDocument(Uri uri) {
        return "com.android.providers.downloads.documents".equals(uri.getAuthority());
    }
}