Android Studio实现文字识别

以下是Android Studio实现文字识别的步骤：

1.在项目的build.gradle文件中添加以下依赖项：

dependencies {
    // ...
    implementation 'com.google.android.gms:play-services-vision:20.1.3'
}

2.在布局文件中添加一个SurfaceView和一个TextView：

<SurfaceView
    android:id="@+id/camera_preview"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<TextView
    android:id="@+id/text_view"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom"
    android:background="#80000000"
    android:padding="16dp"
    android:textColor="#fff"
    android:textSize="18sp" />

3.在MainActivity.java文件中添加以下代码：

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.provider.MediaStore;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.android.gms.vision.Frame;
import com.google.android.gms.vision.text.Text;
import com.google.android.gms.vision.text.TextBlock;
import com.google.android.gms.vision.text.TextRecognizer;

import java.io.IOException;

public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback {

    private static final String TAG = "MainActivity";
    private static final int REQUEST_CAMERA_PERMISSION = 200;
    private static final int REQUEST_IMAGE_CAPTURE = 1;

    private SurfaceView mCameraPreview;
    private TextView mTextView;
    private TextRecognizer mTextRecognizer;

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

        mCameraPreview = findViewById(R.id.camera_preview);
        mTextView = findViewById(R.id.text_view);

        // 检查相机权限
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
                != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.CAMERA},
                    REQUEST_CAMERA_PERMISSION);
        } else {
            startCamera();
        }

        // 初始化文字识别器
        mTextRecognizer = new TextRecognizer.Builder(this).build();
        if (!mTextRecognizer.isOperational()) {
            Log.w(TAG, "Detector dependencies are not yet available.");
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        // 释放文字识别器
        mTextRecognizer.release();
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // 相机预览开始
        startCameraPreview(holder);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        // 相机预览变化
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // 相机预览结束
    }

    private void startCamera() {
        SurfaceHolder holder = mCameraPreview.getHolder();
        holder.addCallback(this);
    }

    private void startCameraPreview(SurfaceHolder holder) {
        try {
            // 打开相机
            Camera camera = Camera.open();
            camera.setPreviewDisplay(holder);
            camera.startPreview();
            // 设置相机预览回调
            camera.setPreviewCallback(new Camera.PreviewCallback() {
                @Override
                public void onPreviewFrame(byte[] data, Camera camera) {
                    // 处理相机预览数据
                    Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
                    detectText(bitmap);
                }
            });
        } catch (IOException e) {
            Log.e(TAG, "Error setting camera preview: " + e.getMessage());
        }
    }

    private void detectText(Bitmap bitmap) {
        // 创建帧
        Frame frame = new Frame.Builder().setBitmap(bitmap).build();
        // 获取文本块
        SparseArray<TextBlock> textBlocks = mTextRecognizer.detect(frame);
        // 处理文本块
        StringBuilder stringBuilder = new StringBuilder();
        for (int i = 0; i < textBlocks.size(); i++) {
            TextBlock textBlock = textBlocks.valueAt(i);
            for (Text text : textBlock.getComponents()) {
                stringBuilder.append(text.getValue());
                stringBuilder.append("\n");
            }
        }
        // 显示识别结果
        mTextView.setText(stringBuilder.toString());
    }

    public void takePicture(View view) {
        // 拍照
        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        if (intent.resolveActivity(getPackageManager()) != null) {
            startActivityForResult(intent, REQUEST_IMAGE_CAPTURE);
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
            // 获取拍摄的照片
            Bundle extras = data.getExtras();
            Bitmap bitmap = (Bitmap) extras.get("data");
            detectText(bitmap);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
                                           @NonNull int[] grantResults) {
        if (requestCode == REQUEST_CAMERA_PERMISSION) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                startCamera();
            } else {
                Toast.makeText(this, "Camera permission denied", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

4.在AndroidManifest.xml文件中添加以下权限：

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

5.运行应用程序并测试文字识别功能。