[英]How to retrieve image from SQLite database in Android Apps Develoment?
假设我有一个由“ D”命名的预填充数据库,其中包含3个字段。 -ID(pk)-名称-图像现在,我想从数据库中检索该图像并尝试在imageview上进行设置。 为此,我使用了3类-MainActivity.java
-Student.java
-PrepopuDB.java
我的这三个类的代码: MainActivity.java
package com.example.db_image;
import java.util.ArrayList;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
TextView tvName;
Button btn;
ImageView iv;
private PrePopuDB pdb;
ArrayList<Student> all;
int i = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initialize();
all = pdb.getAllInfo();
}
void initialize(){
tvName = (TextView)findViewById(R.id.textView2);
btn = (Button)findViewById(R.id.button1);
iv = (ImageView)findViewById(R.id.imageView1);
pdb = new PrePopuDB(getApplicationContext());
}
public void show(View v){
Student std = all.get(i);
tvName.setText(std.getName());
iv.setImageBitmap(getPhoto(std.getPh())); // Try to set bitmap image to imageview
i++;
}
private Bitmap getPhoto(byte[] phot){// this function try to convert byte array to Bitmap image. And return bitmap image.
return BitmapFactory.decodeByteArray(phot, 0, phot.length);
}
}
PrepopuDB.java
package com.example.db_image;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
public class PrePopuDB extends SQLiteOpenHelper {
public static final String DB_NAME = "D";
public static final String Table_NAME = "T";
public static final String ID = "id";
public static final String NAME = "name";
public static String DB_PATH;
public static final String PH = "photo";
Context context;
private SQLiteDatabase database;
public PrePopuDB(Context context) {
super(context, DB_NAME, null, 1);
this.context = context;
String packageName = context.getPackageName();
DB_PATH = "/data/data/" + packageName + "/databases/";
this.database = openDB();
}
public synchronized void close() {
if (this.database != null) {
this.database.close();
}
}
public SQLiteDatabase openDB() {
String path = DB_PATH + DB_NAME;
if (database == null) {
createDB();
database = SQLiteDatabase.openDatabase(path, null,
SQLiteDatabase.OPEN_READWRITE);
}
return database;
}
private void createDB() {
if (!checkDB()) {
this.getReadableDatabase();
copyDB();
} else {
Log.e(getClass().getName(), "DB Exist");
}
}
private void copyDB() {
try {
InputStream is = context.getAssets().open(DB_NAME);
String path = DB_PATH + DB_NAME;
OutputStream op = new FileOutputStream(path);
byte[] buffer = new byte[4096];
int readcount = 0;
while ((readcount = is.read(buffer)) > 0) {
op.write(buffer, 0, readcount);
}
is.close();
op.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public boolean checkDB() {
String path = DB_PATH + DB_NAME;
File file = new File(path);
if (file.exists()) {
return true;
} else
return false;
}
public ArrayList<Student> getAllInfo() {
ArrayList<Student> allinfo = new ArrayList<Student>();
// SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = this.database.query(Table_NAME, null, null, null, null,
null, null);
if (cursor != null && cursor.getCount() > 0) {
cursor.moveToFirst();
for (int i = 0; i < cursor.getCount(); i++) {
int id = cursor.getInt(cursor.getColumnIndex(ID));
String name = cursor.getString(cursor.getColumnIndex(NAME));
// Try to get image in binary form
byte[] pho = cursor.getBlob(cursor.getColumnIndex(PH));
Student std = new Student(id, name, pho);
allinfo.add(std); // store student class in array list
cursor.moveToNext();
}
}
cursor.close();
// this.database.close();
return allinfo;
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
学生.java
package com.example.db_image;
import java.sql.Blob;
import android.graphics.Bitmap;
public class Student {
int id;
String name;
// little bit confused about data type
//Bitmap ph;
//Blob ph
byte[] ph;
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + "]";
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public byte[] getPh() {
return ph;
}
public Student(int id, String name,byte[] ph) {
super();
this.id = id;
this.name = name;
this.ph = ph;
}
}
我的XML代码如下所示:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.db_image.MainActivity" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Name: " />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/textView1"
android:layout_alignBottom="@+id/textView1"
android:layout_marginLeft="46dp"
android:layout_toRightOf="@+id/textView1"
android:text="Sr7 " />
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textView2"
android:layout_marginTop="20dp"
android:layout_toRightOf="@+id/textView2"
android:src="@drawable/ic_launcher" />
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/imageView1"
android:layout_centerHorizontal="true"
android:layout_marginTop="55dp"
android:text="Button"
android:onClick="show"/>
编写完所有代码后,我的应用程序无法正常运行。 在错误日志上显示
因此,在这里请您帮忙。 消除此类问题的任何帮助均受到高度赞赏。 感谢你 :)
HY,
首先,我不建议将图片保存在数据库中或在不需要时将其保存在内存中。 您应该将其本地存储在图片文件夹中,或者如果不希望将其公开,则将其保存在应用程序的目录中。
然后在数据库中,您应该只将图片的路径存储为String,当您要显示它时,将来自数据库的路径作为字符串,并将其加载到位图对象中,并使用先前加载的位图设置imageview的源图片。
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