我想将图像保存为 sqlite 的路径并检索它然后在 ImageView 上显示

Question

Here is my code:

public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    if (resultCode != RESULT_OK) {
        return;
    }
    ImageButton imageButton = (ImageButton) textEntryView.findViewById(R.id.imageButton);
    imageUri = data.getData();
    showToast(imageUri.getPath());

1. Am I correct about to get the Image Path shown on the Toast?

Here is another one to show on ImageView:

public void setIvImg(String path) {
    this.ivImg.setImageURI(Uri.fromFile(new File(path)));
}

2. Am I correct about showing the image on ImageView?

PS: I already use READ_EXTERNAL_STORAGE permission.

Answer 1

Here's an example that stores the paths in the Database (named itdb) in the table named image_path that has two columns per row _id (an alias of the rowid , so uniquely identifies a row as a long) and image_path which is used for the actual path to the image file.

In this example the images (a few JPG's) have been dropped into the assets folder for simplicity (no need for permissions).

The App when it starts looks at the assets and stores asset file paths that contain .JPG (not anything fancy here). The loadImagePaths method does this.

• Note as the image_path column has been defined with the UNIQUE constraint existing images will be ignored (although an exception will be written to the log).

The handleListView will then extract the rows from the table via a Cursor which is the source data for the SimpleCursorAdapter that is attached to the ListView. Two listeners are set :-

• one for onItemClick , which populates the ImageView.
• the other for onItemLongClick which will delete the entry from the database and then refresh the ListView. (rerunning the App will add any deleted image paths to the database).

With 4 files :-

• MyEnlighten20180927_Consumption.JPG
• MyEnlighten20180927_Overview.JPG
• MyEnlighten20180927_Production.JPG
• MyEnlighten20180927_ProductionGridView.JPG

The the App looks like, when started (no item has been clicked) :-

Clicking an item results in the image being displayed eg :-

The App consists of 3 components, the layout activity_main.xml , the DatabaseHelper DatabaseHelper.java and the Activity MainActivity.java

activity_main.xml

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

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />
    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:background="#FFAAAAFF"
        />

    <ImageView
        android:id="@+id/imageview"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:background="#FFAAFFAA"
        />

</LinearLayout>

DatabaseHelper.java

public class DatabaseHelper extends SQLiteOpenHelper {
    public static final String DBNAME = "itdb";
    public static final int DBVERSION = 1;

    public static final String TBNAME = "image_path";
    public static final String IMAGEPATH_COL_ID = BaseColumns._ID;
    public static final String IMAGEPATH_COL_PATH = "image_path";

    SQLiteDatabase mDB;

    public DatabaseHelper(Context context) {
        super(context, DBNAME, null, DBVERSION);
        mDB = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        String crt_imagepath_table = "CREATE TABLE IF NOT EXISTS " + TBNAME + "(" +
                IMAGEPATH_COL_ID + " INTEGER PRIMARY KEY, " +
                IMAGEPATH_COL_PATH + " TEXT UNIQUE" +
                ")";
        db.execSQL(crt_imagepath_table);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int i, int i1) {

    }

    public long addImagePath(String imagePath) {
        ContentValues cv = new ContentValues();
        cv.put(IMAGEPATH_COL_PATH,imagePath);
        return mDB.insert(TBNAME,null,cv);
    }

    public int deleteImagePathById(long id) {
        String whereclause = IMAGEPATH_COL_ID + "=?";
        String[] whereargs = new String[]{String.valueOf(id)};
        return mDB.delete(TBNAME,whereclause,whereargs);
    }

    public Cursor getImageList() {
        return mDB.query(TBNAME,null,null,null,null,null,null);
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

    String[] mAssetList;
    String mPath = "" ;
    String mImageExtension = ".JPG";
    ListView mLV;
    ImageView mIV;

    DatabaseHelper mDBHlpr;
    Cursor mCsr;
    SimpleCursorAdapter mSCA;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mLV = this.findViewById(R.id.listview);
        mIV = this.findViewById(R.id.imageview);

        mDBHlpr = new DatabaseHelper(this);
        loadImagePaths();
        handleListView();
    }

    /**
     * Handle displaying the ListView, initialising it or refreshing it
     *
     * When initialising the
     */
    private void handleListView() {
        mCsr = mDBHlpr.getImageList();
        if (mSCA == null) {
            mSCA = new SimpleCursorAdapter(
                    this,
                    android.R.layout.simple_list_item_1,mCsr,
                    new String[]{DatabaseHelper.IMAGEPATH_COL_PATH},
                    new int[]{android.R.id.text1},
                    0
            );
            mLV.setAdapter(mSCA);
            mLV.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                    displayImage(mCsr.getString(mCsr.getColumnIndex(DatabaseHelper.IMAGEPATH_COL_PATH)));
                }
            });
            mLV.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
                @Override
                public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
                    mDBHlpr.deleteImagePathById(l);
                    handleListView(); // Refresh Listview as underlying image path has been deleted
                    return true; // indicate event has been handled
                }
            });
        } else {
            mSCA.swapCursor(mCsr);
        }
    }

    @Override
    protected void onDestroy() {
        mCsr.close();
        super.onDestroy();
    }

    private void displayImage(String imagepath) {
        InputStream is = null;
        try {
            is = this.getResources().getAssets().open(imagepath);
        } catch (IOException e) {
            e.printStackTrace();
        }
        Bitmap image = BitmapFactory.decodeStream(is);
        try {
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        mIV.setImageBitmap(image);
    }

    private void loadImagePaths() {
        try {
            mAssetList = this.getAssets().list(mPath);
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }
        for (String s: mAssetList) {
            if (s.contains(mImageExtension)) {
                mDBHlpr.addImagePath(s);
            }
        }
    }
}

This demonstrates the basics of using images with their paths stored in the database.

• Note if using the above then some files with a JPG extension would have to be copied into the assets folder (unless the code is changed to handle a different location).