Android实现选择相册图片并显示功能

package com.example.www.mutilmedia;

import android.Manifest;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;

import java.util.Arrays;

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;

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

    mShowImg = (ImageView) findViewById(R.id.imageView);

  }

  @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;
        Log.e("MainActivity", Arrays.toString(grantResults));
        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_OPEN_DOCUMENT);
      intent.addCategory(Intent.CATEGORY_OPENABLE);
      intent.setType("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());
            Log.e("MainActivity", realPathFromUri);
            showImg(realPathFromUri);
          } else {
            Toast.makeText(this, "图片损坏，请重新选择", Toast.LENGTH_SHORT).show();
          }

          break;
      }
    }
  }


  public void openCamera(View view) {
    ActivityCompat.requestPermissions(MainActivity.this, mPermissionList, 100);
  }


  public void showImg(String path){
    Bitmap bitmap = BitmapFactory.decodeFile(path);
    mShowImg.setImageBitmap(bitmap);
  }

}

package com.example.www.mutilmedia;

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());
  }
}

<?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:context=".MainActivity">

  <ImageView
    android:id="@+id/imageView"
    android:layout_width="0dp"
    android:layout_height="0dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginBottom="8dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/button3"
    app:srcCompat="@android:color/white" />

  <Button
    android:id="@+id/button3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="8dp"
    android:layout_marginTop="16dp"
    android:layout_marginEnd="8dp"
    android:onClick="openCamera"
    android:text="camera"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.048"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="com.example.www.mutilmedia">

  <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

  <application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
      <intent-filter>
        <action android:name="android.intent.action.MAIN" />

        <category android:name="android.intent.category.LAUNCHER" />
      </intent-filter>
    </activity>
  </application>

</manifest>