Android 从相册选择一张图片并返回uri，无需授权任何权限

要直接打开系统相册而不仅仅是最近的图片，你可以使用 Intent.ACTION_PICK 与 ActivityResultContracts.StartActivityForResult结合，而不需要授权任何权限。 核心代码

 imagePickerLauncher = registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->
            val uri: Uri? = result.data?.data
            uri?.let {
                //拿到图片的uri，处理你的业务代码
            }
        }
        
   private fun openGallery() {
        val intent = Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI)
        imagePickerLauncher.launch(intent)
    }
        

MainActivity.kt

import android.content.Intent
import android.graphics.Bitmap
import android.graphics.ImageDecoder
import android.net.Uri
import android.os.Build
import android.os.Bundle
import android.provider.MediaStore
import android.widget.Button
import android.widget.ImageView
import androidx.activity.result.ActivityResultLauncher
import androidx.activity.result.contract.ActivityResultContracts
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    private lateinit var imagePickerLauncher: ActivityResultLauncher<Intent>
    private lateinit var imageView: ImageView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        imageView = findViewById(R.id.imageView)
        val button = findViewById<Button>(R.id.button)

        // Register the launcher to open system gallery
        imagePickerLauncher = registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->
            val uri: Uri? = result.data?.data
            uri?.let {
                displayImage(it)
            }
        }

        // Set button click listener to open gallery
        button.setOnClickListener {
            openGallery()
        }
    }

    private fun openGallery() {
        // Open the system gallery to select an image
        val intent = Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI)
        imagePickerLauncher.launch(intent)
    }

    private fun displayImage(uri: Uri) {
        // Display the selected image in the ImageView
        val bitmap: Bitmap = if (Build.VERSION.SDK_INT < 28) {
            @Suppress("DEPRECATION")
            MediaStore.Images.Media.getBitmap(this.contentResolver, uri)
        } else {
            val source = ImageDecoder.createSource(this.contentResolver, uri)
            ImageDecoder.decodeBitmap(source)
        }
        imageView.setImageBitmap(bitmap)
    }
}

XML 布局文件

在 res/layout/activity_main.xml 中，定义一个 ImageView 和一个 Button：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:contentDescription="@string/app_name" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/imageView"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="16dp"
        android:text="Choose Image" />
</RelativeLayout>