Android 拍照或相册选择照片进行显示缩放位图 Demo

拍照后直接使用 BitmapFactory.decodeStream(...) 进行创建 Bitmap 并显示是有问题的。

Bitmap 是个简单对象，它只存储实际像素数据，也就是说，即使原始照片已压缩过，但存入 Bitmap 对象时，文件并不会同样压缩，导致图片无法显示，所以需要进行缩放位图。

缩放位图代码如下：

PictureUtils.java

package club.seliote.camerademo;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Point;
import android.net.Uri;

import java.io.File;

public class PictureUtils {

    public static Bitmap getScaledBitmap(Uri uri, int destWidth, int destHeight) {
        // read in the dimensions of the image on disk
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(uri.getPath(), options);

        float srcWidth = options.outWidth;
        float srcHeight = options.outHeight;

        // figure out how much to scale down by
        int inSampleSize = 1;
        if (srcWidth > destHeight || srcHeight > destHeight) {
            inSampleSize = Math.round((srcWidth / destWidth) > (srcHeight / destHeight) ? (srcWidth / destWidth) : (srcHeight / destHeight));
        }

        // create a bitmap
        options = new BitmapFactory.Options();
        options.inSampleSize = inSampleSize;
        return BitmapFactory.decodeFile(uri.getPath(), options);
    }

    public static Bitmap getScaledBitmap(Uri uri, Activity activity) {
        Point point = new Point();
        activity.getWindowManager().getDefaultDisplay().getSize(point);
        return PictureUtils.getScaledBitmap(uri, point.x, point.y);
    }

}

拍照并显示的代码:

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="club.seliote.camerademo">

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <provider
            android:name="android.support.v4.content.FileProvider"
            android:authorities="club.seliote.camerademo.fileprovider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths"/>
        </provider>
    </application>

</manifest>

activity_main.xml

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

    <Button
        android:id="@+id/take_photo_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Take a photo"
        android:layout_gravity="center_horizontal"
        android:textAllCaps="false"/>

    <Button
        android:id="@+id/choose_from_album_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Choose from album"
        android:layout_gravity="center_horizontal"
        android:textAllCaps="false"/>

    <ImageView
        android:id="@+id/picture_image_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"/>

</LinearLayout>

xml/file_paths.xml

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android" >
    <external-path
        name="images"
        path="." />
</paths>

MainActivity.java

package club.seliote.camerademo;

import android.Manifest;
import android.annotation.TargetApi;
import android.app.Activity;
import android.content.ContentUris;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.net.Uri;
import android.os.Build;
import android.provider.DocumentsContract;
import android.provider.MediaStore;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v4.content.FileProvider;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.File;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    private static final int CAMERA_INTENT_REQUEST_CODE = 0;
    private static final int ALBUM_INTENT_REQUEST_CODE = 1;

    private static final int WRITE_EXTERNAL_STORAGE_PERMISSION_REQUEST_CODE = 0;

    private String mPictureName;
    private Uri mPictureUri;

    private Button mTakePhotoButton;
    private Button mChooseFromAlbum;
    private ImageView mImageView;

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

        mTakePhotoButton = this.findViewById(R.id.take_photo_button);
        mChooseFromAlbum = this.findViewById(R.id.choose_from_album_button);
        mImageView = this.findViewById(R.id.picture_image_view);

        mTakePhotoButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MainActivity.this.takePhoto();
            }
        });

        mChooseFromAlbum.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, MainActivity.WRITE_EXTERNAL_STORAGE_PERMISSION_REQUEST_CODE);
                } else {
                    MainActivity.this.openAlbum();
                }
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode) {
            case MainActivity.CAMERA_INTENT_REQUEST_CODE :
                if (resultCode == Activity.RESULT_OK) {
                    /*try {
                        // Bitmap is too big to display in screen
                        Bitmap bitmap = BitmapFactory.decodeStream(this.getContentResolver().openInputStream(mPictureUri));
                        mImageView.setImageBitmap(bitmap);
                    } catch (FileNotFoundException exp) {
                        exp.printStackTrace();
                    }*/
                    mImageView.setImageBitmap(PictureUtils.getScaledBitmap(mPictureUri, this));
                }
                break;
            case MainActivity.ALBUM_INTENT_REQUEST_CODE :
                if (resultCode == Activity.RESULT_OK) {
                    this.handlePictureFromAlbum(data);
                }
                break;
            default :
                break;
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode) {
            case MainActivity.WRITE_EXTERNAL_STORAGE_PERMISSION_REQUEST_CODE :
                if (permissions.length > 0 && permissions[0] == Manifest.permission.WRITE_EXTERNAL_STORAGE && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    this.openAlbum();
                } else {
                    Toast.makeText(this, "Permisson deny!", Toast.LENGTH_LONG).show();
                }
        }
    }

    private void takePhoto() {

        // create file
        File file = new File(this.getExternalCacheDir(), mPictureName = (System.currentTimeMillis() + ".jpg"));
        try {
            if (file.exists()) {
                file.delete();
            }
            file.createNewFile();
        } catch (IOException exp) {
            exp.printStackTrace();
        }

        // wrap File to Uri
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            // if version more then API 24, not use true path
            mPictureUri = FileProvider.getUriForFile(this, "club.seliote.camerademo.fileprovider", file);
        } else {
            mPictureUri = Uri.fromFile(file);
        }

        // start camera activity
        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        intent.putExtra(MediaStore.EXTRA_OUTPUT, mPictureUri);
        startActivityForResult(intent, MainActivity.CAMERA_INTENT_REQUEST_CODE);
    }

    private void openAlbum() {
        Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.setType("image/*");
        startActivityForResult(intent, MainActivity.ALBUM_INTENT_REQUEST_CODE);
    }

    // only for Android KitKat(4.4) or later
    @TargetApi(19)
    private void handlePictureFromAlbum(Intent intent) {
        String imagePath = null;
        Uri uri = intent.getData();
        if (DocumentsContract.isDocumentUri(this, uri)) {
            String docId = DocumentsContract.getDocumentId(uri);
            if ("com.android.providers.media.media.documents".equalsIgnoreCase(uri.getAuthority())) {
                String id = docId.split(":")[1];
                String selection = MediaStore.Images.Media.EXTERNAL_CONTENT_URI + "=" + id;
                imagePath = this.getPathFormUri(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, selection);
            } else if ("com.android.providers.downloads.documents".equalsIgnoreCase(uri.getAuthority())) {
                Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"), Long.valueOf(docId));
                imagePath = getPathFormUri(contentUri, null);
            }
        } else if ("content".equalsIgnoreCase(uri.getScheme())) {
            imagePath = this.getPathFormUri(uri, null);
        } else if ("file".equalsIgnoreCase(uri.getScheme())) {
            imagePath = uri.getPath();
        }
        if (imagePath != null) {
            mImageView.setImageBitmap(PictureUtils.getScaledBitmap(Uri.fromFile(new File(imagePath)), this));
        } else {
            Toast.makeText(this, "Filed to get image", Toast.LENGTH_LONG).show();
        }
    }

    @Nullable
    // use uri get picture true path
    private String getPathFormUri(Uri uri, String selection) {
        String path = null;
        Cursor cursor = this.getContentResolver().query(uri, null, selection, null, null);
        if (cursor != null && cursor.moveToFirst()) {
            path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
            cursor.close();
        }
        return path;
    }
}