团队——和谐共生（8）

和谐共生（8）

距离上次发博客的时间有些久了，这次要实现的功能是Android调用系统相册

要实现这一功能，首先加入权限

<uses-permission android:name=”android.permission.INTERNET” />

    <uses-permission android:name=”android.permission.ACCESS_NETWORK_STATE” />

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

<uses-permission android:name=”android.permission.CAMERA” />

编写界面

<?xml version=”1.0″ encoding=”utf-8″?>

<androidx.constraintlayout.widget.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”>

    <Button

        android:id=”@+id/choose_photo”

        android:layout_width=”match_parent”

        android:layout_height=”wrap_content”

        android:layout_marginTop=”10dp”

        android:text=”从相册中选择照片”

        android:textSize=”20sp”

        app:layout_constraintTop_toTopOf=”parent” />

    <ImageView

        android:id=”@+id/picture”

        android:layout_width=”0dp”

        android:layout_height=”wrap_content”

        android:src=”@drawable/shuishan”

        app:layout_constraintBottom_toBottomOf=”parent”

        app:layout_constraintEnd_toEndOf=”parent”

        app:layout_constraintStart_toStartOf=”parent”

        app:layout_constraintTop_toTopOf=”parent” />

</androidx.constraintlayout.widget.ConstraintLayout>

后台代码

package com.example.pictureselect;

import androidx.annotation.NonNull;

import androidx.annotation.Nullable;

import androidx.annotation.RequiresApi;

import androidx.appcompat.app.AppCompatActivity;

import androidx.core.app.ActivityCompat;

import androidx.core.content.ContextCompat;

import android.Manifest;

import android.annotation.SuppressLint;

import android.content.ContentUris;

import android.content.Intent;

import android.content.SharedPreferences;

import android.content.pm.PackageManager;

import android.database.Cursor;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.net.Uri;

import android.os.Build;

import android.os.Bundle;

import android.provider.DocumentsContract;

import android.provider.MediaStore;

import android.view.View;

import android.widget.Button;

import android.widget.ImageView;

import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    public static final int CHOOSE_PHOTO = 2;

    ImageView picture;

    String imagePath = null;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        Button btnChoosePhoto = (Button) findViewById(R.id.choose_photo);

        picture = (ImageView) findViewById(R.id.picture);

        btnChoosePhoto.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                requestPermissino();

            }

        });

        picture.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                requestPermissino();

            }

        });

    }

    private void requestPermissino() {

        if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {

            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);

        }else {

            openAlbum();

        }

    }

    private void openAlbum(){

        Intent intent = new Intent(“android.intent.action.GET_CONTENT”);

        intent.setType(“image/*”);

        startActivityForResult(intent,CHOOSE_PHOTO); //打开相册

    }

    @Override

    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {

        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        switch (requestCode){

            case 1:

                if (grantResults.length>0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){

                    openAlbum();

                }else {

                    Toast.makeText(this,”你拒绝了该权限”,Toast.LENGTH_SHORT).show();

                }

                break;

            default:

                break;

        }

    }

    @Override

    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {

        super.onActivityResult(requestCode, resultCode, data);

        switch (requestCode){

            case CHOOSE_PHOTO:

                if(resultCode == RESULT_OK){

                    //判断手机系统版本号

                    if(Build.VERSION.SDK_INT>=19){

                        //4.4及以上系统使用这个方法处理图片

                        handleImageOnKitKat(data);

                    }

                }

                break;

            default:

                break;

        }

    }

    @RequiresApi(api = Build.VERSION_CODES.KITKAT)

    private void handleImageOnKitKat(Intent data){

        Uri uri = data.getData();

        if(DocumentsContract.isDocumentUri(this,uri)){

            //如果是document类型的Uri，则通过document id处理

            String docId = DocumentsContract.getDocumentId(uri);

            if(“com.android.providers.media.documents”.equals(uri.getAuthority())){

                String id = docId.split(“:”)[1];  //解析出数字格式的id

                String selection = MediaStore.Images.Media._ID+”=”+id;

                imagePath = getImagePath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,selection);

            }else if(“com.android.providers.downloads.documents”.equals(uri.getAuthority())){

                Uri contentUri = ContentUris.withAppendedId(Uri.parse(“content://downloads/public downloads”),Long.valueOf(docId));

                imagePath = getImagePath(contentUri,null);

            }

        }else if(“content”.equalsIgnoreCase(uri.getScheme())){

            //如果是file类型的Uri，直接获取图片路径即可

            imagePath = getImagePath(uri,null);

        }else if(“file”.equalsIgnoreCase(uri.getScheme())){

            //如果是file类型的Uri，直接获取图片路径即可

            imagePath = uri.getPath();

        }

        displayImage(imagePath); //根据图片路径显示图片

    }

    //将选择的图片Uri转换为路径

    @SuppressLint(“Range”)

    private String getImagePath(Uri uri, String selection){

        String path = null;

        //通过Uri和selection来获取真实的图片路径

        Cursor cursor = getContentResolver().query(uri,null,selection,null,null);

        if(cursor!= null){

            if(cursor.moveToFirst()){

                path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));

            }

            cursor.close();

        }

        return path;

    }

    //展示图片

    private void displayImage(String imagePath){

        if(imagePath!=null && !imagePath.equals(“”)){

            Bitmap bitmap = BitmapFactory.decodeFile(imagePath);

            picture.setImageBitmap(bitmap);

            //存储上次选择的图片路径，用以再次打开app设置图片

            SharedPreferences sp = getSharedPreferences(“sp_img”,MODE_PRIVATE);  //创建xml文件存储数据，name:创建的xml文件名

            SharedPreferences.Editor editor = sp.edit(); //获取edit()

            editor.putString(“imgPath”,imagePath);

            editor.apply();

        }else {

            Toast.makeText(this,”获取图片失败”,Toast.LENGTH_SHORT).show();

        }

    }

    @Override

    protected void onResume() {

        super.onResume();

        //设置再次app时显示的图片

        SharedPreferences sp = getSharedPreferences(“sp_img”, MODE_PRIVATE);

        //取出上次存储的图片路径设置此次的图片展示

        String beforeImagePath = sp.getString(“imgPath”, null);

        displayImage(beforeImagePath);

    }

}

到此为止，这个功能就实现了，但不足的是他一次只能获取一张图片，之后会再进行优化。