在我的示例应用程序中，我想从相机和图库中保存图像并保存到sqlite数据库。这是我的代码。
public class MainActivity extends AppCompatActivity {
private static final String TAG = MainActivity.class.getSimpleName();
private static final int GAL_CODE = 24;
private static final int CAM_CODE = 31;
private static final String ALLOW_KEY = "ALLOWED";
private static final String CAMERA_PREF = "camera_pref";
private ImageView imageView;
private EditText nameET, addrET;
private ImageButton galleryBtn, cameraBtn;
private Button saveBtn;
private String address;
private String name;
private DBHelper dbHelper;
private boolean fromCamera = false;
private boolean fromGallery = false;
private Uri outputFileUri;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new DBHelper(this);
imageView = (ImageView) findViewById(R.id.image);
nameET = (EditText) findViewById(R.id.nameET);
addrET = (EditText) findViewById(R.id.addrET);
galleryBtn = (ImageButton) findViewById(R.id.galleryBtn);
cameraBtn = (ImageButton) findViewById(R.id.cameraBtn);
saveBtn = (Button) findViewById(R.id.saveBtn);
galleryBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
selectImage();
}
});
cameraBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
takePhoto();
}
});
saveBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
saveUser();
}
});
}
private void takePhoto() {
File root = new File(Environment.getExternalStorageDirectory() + File.separator + "MyDir" + File.separator);
root.mkdirs();
String fileName = "img_" + System.currentTimeMillis() + ".jpg";
File sdCardImageMainDir = new File(root, fileName);
outputFileUri = Uri.fromFile(sdCardImageMainDir);
List<Intent> cameraIntents = new ArrayList<>();
Intent captureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
PackageManager pm = getPackageManager();
List<ResolveInfo> listCam = pm.queryIntentActivities(captureIntent, 0);
for (ResolveInfo info: listCam){
String packageName = info.activityInfo.packageName;
Intent intent = new Intent(captureIntent);
intent.setComponent(new ComponentName(info.activityInfo.packageName, info.activityInfo.name));
intent.setPackage(packageName);
intent.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri);
cameraIntents.add(intent);
}
startActivityForResult(captureIntent, CAM_CODE);
}
private void saveUser() {
name = nameET.getText().toString();
address = addrET.getText().toString();
if (!address.isEmpty() && !name.isEmpty()){
User user = new User(name, address);
dbHelper.saveInputField(user);
dbHelper.close();
startActivity(new Intent(MainActivity.this, ShowActivity.class));
}
}
private void selectImage() {
Intent intent = new Intent();
intent.setType("image/*");
intent.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(Intent.createChooser(intent, "Select Picture"), GAL_CODE);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == GAL_CODE && resultCode == RESULT_OK){
Uri imgUri = data.getData();
if (imgUri != null){
if(saveImageToDB(imgUri)){
Toast.makeText(this, "Saved Image", Toast.LENGTH_SHORT).show();
}
}
}
if (requestCode == CAM_CODE && resultCode == RESULT_OK){
Bitmap bitmap = (Bitmap) data.getExtras().get("data");
if (bitmap != null){
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, outputStream);
byte[] imageinByte = outputStream.toByteArray();
User user = new User(name, address, imageinByte);
dbHelper.saveInputField(user); // error on this line
}
}
}
这是我的用户模型类。
public class User {
public int id;
public String name;
public String address;
public byte[] image;
public User() {
}
public User(int id) {
this.id = id;
}
public User(String name, String address, byte[] camImage) {
this.name = name;
this.address = address;
this.image = camImage;
}
public User(int id, String name, String address, byte[] camImage) {
this.id = id;
this.name = name;
this.address = address;
this.image = camImage;
}
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 String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public byte[] getImage() {
return image;
}
public void setImage(byte[] image) {
this.image = image;
}
}
我的数据库助手类可以在这里看到：
public class DBHelper {
private static final String DATABASE_NAME = "UsersDemo.db";
private static final int DATABASE_VERSION = 1;
private static final String TABLE_NAME = "profileInfo";
private static final String COL_ID = "databaseId";
private static final String COL_NAME = "name";
private static final String COL_ADDRESS = "addr";
private static final String COL_IMAGE = "image";
private Context mCtx;
private DatabaseManager databaseManager;
private SQLiteDatabase db;
public DBHelper (Context context){
this.mCtx = context;
databaseManager = new DatabaseManager(mCtx);
}
public DBHelper open() throws SQLException{
db = databaseManager.getWritableDatabase();
return this;
}
public void close(){
databaseManager.close();
}
public void saveInputField(User user){
ContentValues values = new ContentValues();
values.put(COL_NAME, user.getName());
values.put(COL_ADDRESS, user.getAddress());
values.put(COL_IMAGE, user.getImage());
db.insert(TABLE_NAME, null, values);
db.close();
}
public User getCurrentUser(int id){
Cursor cursor = db.query(true, TABLE_NAME, new String[]{COL_ID, COL_NAME, COL_ADDRESS}, COL_ID + "=?", new String[]{String.valueOf(id)}, null, null, null, null);
if (cursor != null && cursor.moveToFirst()){
User user = new User(Integer.parseInt(cursor.getString(0)), cursor.getString(1), cursor.getString(2), cursor.getBlob(1));
return user;
}
return null;
}
public void saveCamerayImage(byte[] imageBytes){
ContentValues contentValues = new ContentValues();
contentValues.put(COL_IMAGE, imageBytes);
db.insert(TABLE_NAME, null, contentValues);
}
public void saveGalleryImage(byte[] imageBytes){
ContentValues contentValues = new ContentValues();
contentValues.put(COL_IMAGE, imageBytes);
db.insert(TABLE_NAME, null, contentValues);
}
public byte[] getImage(){
Cursor cursor = db.query(true, TABLE_NAME, new String[]{COL_IMAGE,}, null, null, null, null, COL_ID + " DESC", "1");
if (cursor.moveToFirst()){
byte[] blob = cursor.getBlob(cursor.getColumnIndex(COL_IMAGE));
cursor.close();
return blob;
}
cursor.close();
Toast.makeText(mCtx, "No Image Found", Toast.LENGTH_SHORT).show();
return null;
}
public class DatabaseManager extends SQLiteOpenHelper {
public DatabaseManager(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
String db_create = "Create Table " + TABLE_NAME + " ("
+ COL_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ COL_NAME + " TEXT, "
+ COL_ADDRESS + " TEXT, "
+ COL_IMAGE + " BLOB NOT NULL );";
sqLiteDatabase.execSQL(db_create);
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
sqLiteDatabase.execSQL("DROP TABLE IF EXISTS" + TABLE_NAME);
onCreate(sqLiteDatabase);
}
}
}
在运行应用程序时，我在logcat中收到此错误消息。我似乎无法理解为什么它会显示出来。
我的logcat如下：
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'long android.database.sqlite.SQLiteDatabase.insert(java.lang.String, java.lang.String, android.content.ContentValues)' on a null object reference
at com.joey.example.dbsqlite.DBHelper.saveInputField(DBHelper.java:53)
at com.joey.example.dbsqlite.MainActivity.onActivityResult(MainActivity.java:170)
at android.app.Activity.dispatchActivityResult(Activity.java:6919)
at android.app.ActivityThread.deliverResults(ActivityThread.java:4184)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:4231)
at android.app.ActivityThread.-wrap20(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:203)
at android.app.ActivityThread.main(ActivityThread.java:6269)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1063)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:924)
有人可以解释如何解决此错误吗？感谢。
答案 0 :(得分：0)
在写入数据库时，您忘记在方法中调用open（）
databaseManager.getWritableDatabase()允许您写入数据库的权限。
我也觉得在调用方法时不需要返回DBHelper。更改此内容
public DBHelper open() throws SQLException {
db = databaseManager.getWritableDatabase();
return this;
}
答案 1 :(得分：0)
将图像保存到sqlite是个坏主意，但是如果你还想继续下去，这里有代码
public static void insertPicture(byte[] data)
{
SQLiteDatabase db = thisAct.openOrCreateDatabase(ConstantCodes.IMAGE_DATABASE, 2, null);
ContentValues values = new ContentValues(1);
values.put("photo", data);
db.insert("photos", null, values);
db.close();
}
快乐的编码!!
答案 2 :(得分：0)
您需要致电
db = databaseManager.getWritableDatabase();
在saveInputField之前，对db对象做任何事情。处理db