android sqlite 存图片示例

以下是一个完整的 Android SQLite 存储图片的示例代码：

1. 在 layout 目录下创建一个名为 activity_main.xml 的布局文件，添加一个 ImageView 和一个 Button：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/image_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:adjustViewBounds="true"
        android:scaleType="centerCrop"
        android:src="@drawable/placeholder" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="Choose Image" />

</RelativeLayout>

2. 在 MainActivity.java 中实现图片的存储和显示逻辑：

public class MainActivity extends AppCompatActivity {

    private ImageView imageView;
    private Button button;
    private Bitmap selectedBitmap;

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

        imageView = findViewById(R.id.image_view);
        button = findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                startActivityForResult(intent, 1);
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == 1 && resultCode == RESULT_OK && data != null) {
            Uri uri = data.getData();
            try {
                selectedBitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), uri);
                imageView.setImageBitmap(selectedBitmap);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public void saveImage(View view) {
        if (selectedBitmap != null) {
            SQLiteDatabase db = openOrCreateDatabase("MyDatabase", Context.MODE_PRIVATE, null);
            db.execSQL("CREATE TABLE IF NOT EXISTS Images (Name VARCHAR, Data BLOB)");
            ContentValues values = new ContentValues();
            values.put("Name", "test");
            ByteArrayOutputStream stream = new ByteArrayOutputStream();
            selectedBitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);
            byte[] byteArray = stream.toByteArray();
            values.put("Data", byteArray);
            db.insert("Images", null, values);
            db.close();
            Toast.makeText(this, "Image saved to database", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(this, "No image selected", Toast.LENGTH_SHORT).show();
        }
    }

    public void loadImage(View view) {
        SQLiteDatabase db = openOrCreateDatabase("MyDatabase", Context.MODE_PRIVATE, null);
        Cursor cursor = db.rawQuery("SELECT * FROM Images WHERE Name='test'", null);
        if (cursor.moveToFirst()) {
            byte[] byteArray = cursor.getBlob(1);
            Bitmap bitmap = BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);
            imageView.setImageBitmap(bitmap);
        } else {
            Toast.makeText(this, "Image not found in database", Toast.LENGTH_SHORT).show();
        }
        cursor.close();
        db.close();
    }
}

3. 在 AndroidManifest.xml 中添加读取外部存储权限：

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

在运行应用程序时，点击 Choose Image 按钮可以选择图片并在 ImageView 中显示。点击 Save Image 按钮将所选图片存储到 SQLite 数据库中，点击 Load Image 按钮从数据库中读取图片并在 ImageView 中显示。