Android位图/缩略图缩放

Question

我正在根据我正在处理的屏幕大小生成图像视图。我试图为缩略图放置一个占位符。在用户拍照后，将其放置在该占位符内并缩放以适合。我不确定这是否是缩放缩略图图像的正确方法。有没有人做过类似的事情？

CameraActivity：

import android.content.Context;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.drawable.ColorDrawable;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.text.method.ScrollingMovementMethod;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.view.inputmethod.InputMethodManager;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.Scroller;

import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class CameraActivity extends AppCompatActivity {
    private static final String TAG = "CameraActivty";
    static final int REQUEST_IMAGE_CAPTURE = 1;
    private ImageView mImageThumb;
    private Button cameraButton;
    private EditText note;
    private RelativeLayout layout;
    private String mCurrentPhotoPath;
    private File photoFile;
    private int targetW;
    private int targetH;
    InputMethodManager in;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera);
        ColorDrawable colorDrawable = new ColorDrawable(Color.parseColor("#000000"));
        getSupportActionBar().setBackgroundDrawable(colorDrawable);
        this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LOCKED);

        in = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
        layout = (RelativeLayout) findViewById(R.id.cameraRelLayout);
        mImageThumb = (ImageView) findViewById(R.id.imageThumb);
        getScreenSize();

        mImageThumb.getLayoutParams().height = targetH;
        mImageThumb.getLayoutParams().width = targetW;


        cameraButton = (Button) findViewById(R.id.pictureButton);
        note = (EditText) findViewById(R.id.note);
        note.setScroller(new Scroller(this));
        note.setMaxLines(1);
        note.setVerticalScrollBarEnabled(true);
        note.setMovementMethod(new ScrollingMovementMethod());

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

        layout.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View view, MotionEvent motionEvent) {
                hideKeyboard(view);
                return false;
            }
        });

        note.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View view, MotionEvent motionEvent) {
                showKeyboard(view);
                return false;
            }
        });
    }

    private void getScreenSize(){
        DisplayMetrics display = this.getResources().getDisplayMetrics();
        int screenWidth = display.widthPixels;
        targetW = screenWidth - (screenWidth / 8);
        targetH = (targetW * 3) / 4;
    }

    private File createImageFile() throws IOException {
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        String imageFileName = "JPEG_" + timeStamp + "_";
        File storageDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
        File image = File.createTempFile(imageFileName, ".jpg", storageDir);
        mCurrentPhotoPath = image.getAbsolutePath();
        return image;
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
            setPic();
        }
    }

    private void dispatchTakePictureIntent() {
        Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
            photoFile = null;
            try {
                photoFile = createImageFile();
            } catch (IOException ex) {
                // Error occurred while creating the File
            }
            if (photoFile != null) {
                takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(photoFile));
                startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
            }
        }
    }

    private void setPic() {
        BitmapFactory.Options bmOptions = new BitmapFactory.Options();        
        BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions);
        int photoW = bmOptions.outWidth;
        int photoH = bmOptions.outHeight;
        int scaleFactor = Math.min(photoW/targetW, photoH/targetH);

        bmOptions.inJustDecodeBounds = false;
        bmOptions.inSampleSize = scaleFactor;
        mImageThumb.setImageBitmap(rotateBitmap(bmOptions));
    }

    public Bitmap rotateBitmap(BitmapFactory.Options ops){
        Matrix matrix = new Matrix();
        matrix.postRotate(90);
        Bitmap bitmap = BitmapFactory.decodeFile(mCurrentPhotoPath, ops);
        Bitmap scaledMap = Bitmap.createScaledBitmap(bitmap, targetW, targetH, true);
        Bitmap rotatedMap = Bitmap.createBitmap(scaledMap, 0, 0, scaledMap.getWidth(), scaledMap.getHeight(), matrix, true);
        return rotatedMap;
    }

    public void hideKeyboard(View view) {
        in.hideSoftInputFromWindow(view.getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);
    }

    public void showKeyboard(View view) {
        in.showSoftInput(view, InputMethodManager.SHOW_IMPLICIT);
    }

    @Override
    protected void onResume() {
        super.onResume();
        this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    }
}

CameraXML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:focusableInTouchMode="true"
    android:id="@+id/cameraRelLayout">

    <ImageView
        android:layout_marginTop="25dp"
        android:layout_width="250dp"
        android:layout_height="250dp"
        android:background="@drawable/image_holder"
        android:layout_centerHorizontal="true"
        android:id="@+id/imageThumb"
        />

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:layout_marginTop="50dp"
    android:layout_alignParentBottom="true">

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="textMultiLine"
        android:enabled="true"
        android:minLines="2"
        android:textIsSelectable="true"
        android:focusable="true"
        android:isScrollContainer="true"
        android:layout_weight="1"
        android:gravity="top"
        android:padding="10dp"
        android:ems="10"
        android:hint="Problem Description"
        android:layout_marginBottom="15dp"
        android:id="@+id/note"
         />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Take Picture"
        android:id="@+id/pictureButton"
        android:background="@drawable/default_button"
        android:layout_gravity="center_horizontal"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_margin="8dp" />
</LinearLayout>

</RelativeLayout>