android - 有时未在 imageview 中设置位图图像

Question

我使用简单的一键和图像视图，我从图像视图中设置的相机图像中获取图片，有时成功地在图像视图中设置位图图像有时没有在图像中设置位图图像，我通过错误空指针异常，我正在使用移动version 9.0（Redmi 8A）和安卓version 10运行完美。这是为什么？

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import androidx.core.content.FileProvider;
import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;
import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

public class Cameratest extends AppCompatActivity {

private Button button;
private ImageView imageView;

public static final int REQUEST_IMAGE = 100;
public static final int REQUEST_PERMISSION = 200;
private String imageFilePath = "";

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

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

    if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) !=
            PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(this, new String[] {Manifest.permission.WRITE_EXTERNAL_STORAGE},
                REQUEST_PERMISSION);
    }

    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            openCameraIntent();
        }
    });

}

private void openCameraIntent() {
    Intent pictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    if (pictureIntent.resolveActivity(getPackageManager()) != null) {

        File photoFile = null;
        try {
            photoFile = createImageFile();
        }
        catch (IOException e) {
            e.printStackTrace();
            return;
        }
        Uri photoUri = FileProvider.getUriForFile(this, getPackageName() +".provider", photoFile);
        pictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, photoUri);
        startActivityForResult(pictureIntent, REQUEST_IMAGE);
    }
}

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

    if (requestCode == REQUEST_PERMISSION && grantResults.length > 0) {
        if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            Toast.makeText(this, "Thanks for granting Permission", Toast.LENGTH_SHORT).show();
        }
    }
}

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

    if (requestCode == REQUEST_IMAGE) {
        if (resultCode == RESULT_OK) {
            imageView.setImageURI(Uri.parse(imageFilePath));
        }
        else if (resultCode == RESULT_CANCELED) {
            Toast.makeText(this, "You cancelled the operation", Toast.LENGTH_SHORT).show();
        }
    }
}

private File createImageFile() throws IOException{

    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.getDefault()).format(new Date());
    String imageFileName = "IMG_" + timeStamp + "_";
    File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
    File image = File.createTempFile(imageFileName, ".jpg", storageDir);
    imageFilePath = image.getAbsolutePath();

    return image;
}

}

标签： androidimagebitmapcameraimageview

Answer 1

public static final String FILE_NAME = "temp.jpg";

设置图像onActivityResult

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

    if (requestCode == REQUEST_IMAGE) {
        if (resultCode == RESULT_OK) {
         try {
                Uri photoUri = FileProvider.getUriForFile(this, getApplicationContext().getPackageName() + ".provider", getCameraFile());
                Bitmap bitmap =
                    scaleBitmapDown(
                            MediaStore.Images.Media.getBitmap(getContentResolver(), photoUri),
                            1200);
                mImageView.setImageBitmap(bitmap);
          } catch (IOException e) {
             e.printStackTrace();
         }
        }
        else if (resultCode == RESULT_CANCELED) {
            Toast.makeText(this, "You cancelled the operation", Toast.LENGTH_SHORT).show();
        }
    }
}

启动相机意图

Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
            Uri photoUri = FileProvider.getUriForFile(this, getApplicationContext().getPackageName() + ".provider", getCameraFile());
            intent.putExtra(MediaStore.EXTRA_OUTPUT, photoUri);
            intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
            startActivityForResult(intent, REQUEST_IMAGE);

创建相机文件

public File getCameraFile() {
    File dir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
    return new File(dir, FILE_NAME);
}

缩小位图

private Bitmap scaleBitmapDown(Bitmap bitmap, int maxDimension) {

    int originalWidth = bitmap.getWidth();
    int originalHeight = bitmap.getHeight();
    int resizedWidth = maxDimension;
    int resizedHeight = maxDimension;

    if (originalHeight > originalWidth) {
        resizedHeight = maxDimension;
        resizedWidth = (int) (resizedHeight * (float) originalWidth / (float) originalHeight);
    } else if (originalWidth > originalHeight) {
        resizedWidth = maxDimension;
        resizedHeight = (int) (resizedWidth * (float) originalHeight / (float) originalWidth);
    } else if (originalHeight == originalWidth) {
        resizedHeight = maxDimension;
        resizedWidth = maxDimension;
    }
    return Bitmap.createScaledBitmap(bitmap, resizedWidth, resizedHeight, false);
}