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java - 如何在 Android 应用程序开发中从 SQLite 数据库检索图像?

转载 作者:行者123 更新时间:2023-12-01 11:16:42 27 4
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假设我有名为“D”的预填充数据库,其中包含 3 个字段。 - ID(pk) - 姓名 - 图像现在我想从数据库检索此图像并尝试在 imageview 上设置。为此我使用了 3 Class - MainActivity.java
- Student.java
- PrepopuDB.java

我的这 3 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

}

}

Student.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"/>

写完所有这些代码后,我的应用程序无法正常工作。错误日志上显示 enter image description here

所以我在这里请求你的帮助。任何有助于摆脱这个问题的帮助都将受到高度赞赏。谢谢你:)

最佳答案

嘿,

首先,如果没有必要,我不建议将图片保存在数据库中或将其保留在内存中。您应该将其本地存储在图片文件夹中,或者如果您不希望其公开,请将其保存在应用程序的目录中。

然后在数据库中,您应该仅将图片的路径存储为字符串,当您想要显示它时,将数据库中的路径作为字符串并将其加载到位图对象中,并使用之前加载的位图设置 imageview 的源图片。

关于java - 如何在 Android 应用程序开发中从 SQLite 数据库检索图像?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31743226/

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