Android 有时不在imageview中设置位图图像

我使用简单的一个按钮和图像视图，我在图像视图中设置相机图像，有时在图像视图中成功设置位图图像，有时在图像视图中未设置位图图像，我经历了错误空指针异常，我使用移动

版本9.0

（Redmi 8A）和android

版本10

工作正常。为什么呢

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;
}

}

在ActivityResult上设置图像

@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);
}

---

发布来自

LogCat

的错误，不要转到活动结果有时通过编辑问题发布来自

LogCat

的错误…跳过46帧！应用程序可能在其主线程上做了太多工作。V/FA:活动已恢复，时间：347404464 V/FA:屏幕暴露时间少于1000毫秒。事件未发送。时间：145 V/FA：活动暂停，时间：347404597与目标VM断开连接，地址：'localhost:8600'，传输：'socket'Use

Picasso Library

将

Image

设置为

ImageView

。这可能很好。添加了什么文件名和scalebitmadown

scalebitmadown（）

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);
}