嘿，我在创建 Android 应用程序方面有点菜鸟，这只是我的第二个。我需要创建一个应用程序来扫描条形码并将信息保存到数据库中。
我使用 zxing 条码扫描仪和 Sqllite 数据库创建了一个产品数据库，如本文Zxing 应用程序和 SQLite 数据库中所述。但是，当我在填写产品表格后单击添加产品按钮时。弹出一个消息框说我的应用程序不幸停止了。扫描和填充工作但我认为数据库操作不起作用。
这是我添加产品表单和数据库操作的页面。
开始菜单.java
package com.example.barcodedatabaseapp;
import java.math.BigDecimal;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class StartMenu extends Activity {
static final class ProductData {
String barcode;
String format;
String title;
String Others;
BigDecimal Price;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start_menu);
Button addButton=(Button) findViewById(R.id.button1);
addButton.setOnClickListener(new OnClickListener(){
public void onClick(View v)
{
startActivity(new Intent(StartMenu.this,AddProduct.class));
}
});
}
}
添加产品.java
package com.example.barcodedatabaseapp;
import java.math.BigDecimal;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import com.example.barcodeda tabaseapp.StartMenu.ProductData;
public class AddProduct extends Activity implements OnClickListener {
private static final int REQUEST_BARCODE = 0;
private static final ProductData mProductData = new ProductData();
EditText mBarcodeEdit;
EditText mFormatEdit;
EditText mTitleEdit;
EditText mPriceEdit;
private Button mScanButton;
private Button mAddButton;
ProductDatabase mProductDb;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_product);
mBarcodeEdit = (EditText) findViewById(R.id.barcodeEdit);
mFormatEdit = (EditText) findViewById(R.id.codeFormatEdit);
mTitleEdit = (EditText) findViewById(R.id.titleEdit);
mPriceEdit = (EditText) findViewById(R.id.priceEdit);
mScanButton = (Button) findViewById(R.id.scanButton);
mScanButton.setOnClickListener(this);
mAddButton = (Button) findViewById(R.id.addButton2);
mAddButton.setOnClickListener(this);
}
public void onClick(View v) {
switch (v.getId()) {
case R.id.scanButton:
Intent intent = new Intent("com.google.zxing.client.android.SCAN");
intent.putExtra("SCAN_MODE", "PRODUCT_MODE");
startActivityForResult(intent, REQUEST_BARCODE);
break;
case R.id.addButton2:
String barcode = mBarcodeEdit.getText().toString();
String format = mFormatEdit.getText().toString();
String title = mTitleEdit.getText().toString();
String price = mPriceEdit.getText().toString();
String errors = validateFields(barcode, format, title, price);
if (errors.length() > 0) {
showInfoDialog(this, "Please fix errors", errors);
} else {
mProductData.barcode = barcode;
mProductData.format = format;
mProductData.title = title;
mProductData.Price = new BigDecimal(price);
mProductDb.insert(mProductData);
showInfoDialog(this, "Success", "Product saved successfully");
resetForm();
}
break;
}
}
private void showInfoDialog(Context context, String title, String information) {
new AlertDialog.Builder (context)
.setMessage(information)
.setTitle(title)
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
}).show();
}
private void resetForm() {
mBarcodeEdit.getText().clear();
mFormatEdit.getText().clear();
mTitleEdit.getText().clear();
mPriceEdit.getText().clear();
}
public void onActivityResult(int requestCode, int resultCode, Intent intent) {
if (requestCode == REQUEST_BARCODE) {
if (resultCode == RESULT_OK) {
String barcode = intent.getStringExtra("SCAN_RESULT");
mBarcodeEdit.setText(barcode);
String format = intent.getStringExtra("SCAN_RESULT_FORMAT");
mFormatEdit.setText(format);
} else if (resultCode == RESULT_CANCELED) {
finish();
}
}
}
private static String validateFields(String barcode, String format,
String title, String price) {
StringBuilder errors = new StringBuilder();
if (barcode.matches("^\\s*$")) {
errors.append("Barcode required\n");
}
if (format.matches("^\\s*$")) {
errors.append("Format required\n");
}
if (title.matches("^\\s*$")) {
errors.append("Title required\n");
}
if (!price.matches("^-?\\d+(.\\d+)?$")) {
errors.append("Need numeric price\n");
}
return errors.toString();
}
}
产品数据库.java
package com.example.barcodedatabaseapp;
import java.math.BigDecimal;
import com.example.barcodedatabaseapp.StartMenu.ProductData;
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class ProductDatabase {
private static final String PRODUCT_TABLE="products";
private static final String DATABASE_NAME="spot_pay.db";
private static final int DATABASE_VERSION=1;
private static final BigDecimal ONE_HUNDRED =new BigDecimal(100);
private SQLiteDatabase db;
private static class ProductDatabaseHelper extends SQLiteOpenHelper {
private static final String TAG = null;
public ProductDatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
StringBuilder sql = new StringBuilder();
sql.append("create table ").append(PRODUCT_TABLE)
.append("( ")
.append(" _id integer primary key,")
.append(" barcode text,")
.append(" format text,")
.append(" title text,")
.append(" price currency")
.append(") ");
db.execSQL(sql.toString());
Log.d(TAG, PRODUCT_TABLE + "table created");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("drop table if exists " + PRODUCT_TABLE);
onCreate(db);
}
}
public ProductDatabase(Context context) {
ProductDatabaseHelper helper = new ProductDatabaseHelper(context);
db = helper.getWritableDatabase();
}
public boolean insert(ProductData product) {
ContentValues vals = new ContentValues();
vals.put("barcode", product.barcode);
vals.put("format", product.format);
vals.put("title", product.title);
vals.put("price", product.Price.multiply(ONE_HUNDRED).longValue());
return db.insert(PRODUCT_TABLE, null, vals) != -1;
}
}
在 xml 文件中有关于硬编码文本字符串的警告，但在 eclipse 中没有错误。
这是 logcat，请注意我的模拟器无法识别我的网络摄像头，我填写了我在兄弟的 Nexus 10 上运行的表格。
06-06 09:26:42.840: E/AndroidRuntime(825): FATAL EXCEPTION: main
06-06 09:26:42.840: E/AndroidRuntime(825): android.content.ActivityNotFoundException: No Activity found to handle Intent { act=com.google.zxing.client.android.SCAN (has extras) }
06-06 09:26:42.840: E/AndroidRuntime(825): at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1622)
06-06 09:26:42.840: E/AndroidRuntime(825): at android.app.Instrumentation.execStartActivity(Instrumentation.java:1417)
06-06 09:26:42.840: E/AndroidRuntime(825): at android.app.Activity.startActivityForResult(Activity.java:3370)
06-06 09:26:42.840: E/AndroidRuntime(825): at android.app.Activity.startActivityForResult(Activity.java:3331)
06-06 09:26:42.840: E/AndroidRuntime(825): at com.example.barcodedatabaseapp.AddProduct.onClick(AddProduct.java:51)
06-06 09:26:42.840: E/AndroidRuntime(825): at android.view.View.performClick(View.java:4202)
06-06 09:26:42.840: E/AndroidRuntime(825): at android.view.View$PerformClick.run(View.java:17340)
06-06 09:26:42.840: E/AndroidRuntime(825): at android.os.Handler.handleCallback(Handler.java:725)
06-06 09:26:42.840: E/AndroidRuntime(825): at android.os.Handler.dispatchMessage(Handler.java:92)
06-06 09:26:42.840: E/AndroidRuntime(825): at android.os.Looper.loop(Looper.java:137)
06-06 09:26:42.840: E/AndroidRuntime(825): at android.app.ActivityThread.main(ActivityThread.java:5039)
06-06 09:26:42.840: E/AndroidRuntime(825): at java.lang.reflect.Method.invokeNative(Native Method)
06-06 09:26:42.840: E/AndroidRuntime(825): at java.lang.reflect.Method.invoke(Method.java:511)
06-06 09:26:42.840: E/AndroidRuntime(825): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
06-06 09:26:42.840: E/AndroidRuntime(825): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
06-06 09:26:42.840: E/AndroidRuntime(825): at dalvik.system.NativeStart.main(Native Method)
还
06-06 09:28:38.579: E/AndroidRuntime(864): FATAL EXCEPTION: main
06-06 09:28:38.579: E/AndroidRuntime(864): java.lang.NullPointerException
06-06 09:28:38.579: E/AndroidRuntime(864): at com.example.barcodedatabaseapp.AddProduct.onClick(AddProduct.java:70)
06-06 09:28:38.579: E/AndroidRuntime(864): at android.view.View.performClick(View.java:4202)
06-06 09:28:38.579: E/AndroidRuntime(864): at android.view.View$PerformClick.run(View.java:17340)
06-06 09:28:38.579: E/AndroidRuntime(864): at android.os.Handler.handleCallback(Handler.java:725)
06-06 09:28:38.579: E/AndroidRuntime(864): at android.os.Handler.dispatchMessage(Handler.java:92)
06-06 09:28:38.579: E/AndroidRuntime(864): at android.os.Looper.loop(Looper.java:137)
06-06 09:28:38.579: E/AndroidRuntime(864): at android.app.ActivityThread.main(ActivityThread.java:5039)
06-06 09:28:38.579: E/AndroidRuntime(864): at java.lang.reflect.Method.invokeNative(Native Method)
06-06 09:28:38.579: E/AndroidRuntime(864): at java.lang.reflect.Method.invoke(Method.java:511)
06-06 09:28:38.579: E/AndroidRuntime(864): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
06-06 09:28:38.579: E/AndroidRuntime(864): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
06-06 09:28:38.579: E/AndroidRuntime(864): at dalvik.system.NativeStart.main(Native Method)