【发布时间】：2015-05-20 16:50:15
【问题描述】：
当我尝试从表中删除一行时遇到问题，当我创建一个 JSON 文件以将表的数据保存在那里时出现了这个问题。一切正常，除非我按下删除图标，然后该行仍然存在。我将在下面发布 mainactivity 类和数据库类。 如果您能帮助我，我将不胜感激。
public class MainActivity extends Activity {
LinearLayout mainLayout=null;
EditText name=null,brand=null,cost=null;
Button insertRecord=null,showRecords=null;
Button orderbyname=null,orderbybrand=null,orderbycost=null;
ArrayList<Car> result=new ArrayList<Car>();
TableLayout resultLayout=null;
Database db=null;
LinearLayout jsonLayout=null;
Button loadJSON=null,saveJSON=null;
public void makeJSON()
{
jsonLayout=new LinearLayout(this);
mainLayout.addView(jsonLayout);
loadJSON=new Button(this);
loadJSON.setText("LOAD JSON");
jsonLayout.addView(loadJSON);
loadJSON.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v) {
AlertDialog.Builder alert = new
AlertDialog.Builder(MainActivity.this);
alert.setTitle("Load FILE");
alert.setMessage("Specify file name: ");
final EditText input = new EditText(MainActivity.this);
alert.setView(input);
alert.setPositiveButton("Ok",
new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int whichButton)
{
String value = input.getText().toString();
File myfile=new File(
Environment.getExternalStorageDirectory(),value);
try {
BufferedReader br = new BufferedReader(
new InputStreamReader(new
FileInputStream(myfile), "utf8"),65536);
String line="";
line=br.readLine();
try {
JSONArray x=new JSONArray(line);
Log.d("TEST","I have read "+x);
int i;
db.clearData();
for(i=0;i<x.length();i++)
{
JSONObject p=x.getJSONObject(i);
String name=p.getString("name");
String brand=p.getString("brand");
double cost =p.getDouble("cost");
db.insert(name, brand, cost);
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
br.close();
}catch(IOException e)
{
Log.d("TEST",e.getMessage());
}
}});
alert.setNegativeButton("Cancel", new
DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton)
{
}
});
alert.show();
}
});
saveJSON=new Button(this);
saveJSON.setText("SAVE JSON");
saveJSON.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v) {
result=db.getResults();
final JSONArray x=new JSONArray();
int i;
for(i=0;i<result.size();i++)
{
JSONObject p=new JSONObject();
try {
p.put("name", result.get(i).name);
p.put("brand",result.get(i).brand);
p.put("cost", result.get(i).cost);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
x.put(p);
}
String s=x.toString();
AlertDialog.Builder alert = new
AlertDialog.Builder(MainActivity.this);
alert.setTitle("Create FILE");
alert.setMessage("Specify file name: ");
final EditText input = new EditText(MainActivity.this);
alert.setView(input);
alert.setPositiveButton("Ok",
new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int whichButton)
{
String value = input.getText().toString();
File myfile=new File(
Environment.getExternalStorageDirectory(),value);
try {
Writer out = new BufferedWriter(new OutputStreamWriter(
new FileOutputStream(myfile), "UTF8"));
out.append(x.toString());
out.flush();
out.close();
Log.d("TEST", "Write "+x);
}catch(IOException e)
{
Log.d("TEST",e.getMessage());
}
}});
alert.setNegativeButton("Cancel", new
DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton)
{
}
});
alert.show();
}
});
jsonLayout.addView(saveJSON);
}
public void makeInputs()
{
LinearLayout l1=new LinearLayout(this);
mainLayout.addView(l1);
name=new EditText(this);
name.setHint("Car name");
l1.addView(name);
brand=new EditText(this);
brand.setHint("Car brand");
l1.addView(brand);
cost=new EditText(this);
cost.setHint("Car cost");
l1.addView(cost);
}
public void makeButtons()
{
LinearLayout l2=new LinearLayout(this);
mainLayout.addView(l2);
insertRecord=new Button(this);
insertRecord.setText("INSERT RECORD");
l2.addView(insertRecord);
showRecords=new Button(this);
showRecords.setText("SHOW RECORDS");
l2.addView(showRecords);
insertRecord.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v) {
db.insert(name.getText().toString(),
brand.getText().toString(),
Double.parseDouble(cost.getText().toString()));
}
});
showRecords.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v) {
result=db.getResults();
updateTable();
}
});
}
public void makeTable()
{
resultLayout=new TableLayout(this);
ScrollView scroll=new ScrollView(this);
mainLayout.addView(scroll);
scroll.addView(resultLayout);
TableRow r1=new TableRow(this);
resultLayout.addView(r1);
orderbyname=new Button(this);
orderbyname.setText("NAME");
r1.addView(orderbyname);
orderbybrand=new Button(this);
orderbybrand.setText("BRAND");
r1.addView(orderbybrand);
orderbycost=new Button(this);
orderbycost.setText("COST");
r1.addView(orderbycost);
orderbyname.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v) {
int i,j;
for(i=0;i<result.size();i++)
{
for(j=0;j<result.size()-1;j++)
{
Car c1=result.get(j);
Car c2=result.get(j+1);
if(c1.name.compareTo(c2.name)<0)
{
result.set(j, c2);
result.set(j+1, c1);
}
}
}
updateTable();
}
});
orderbybrand.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v) {
int i,j;
for(i=0;i<result.size();i++)
{
for(j=0;j<result.size()-1;j++)
{
Car c1=result.get(j);
Car c2=result.get(j+1);
if(c1.brand.compareTo(c2.brand)<0)
{
result.set(j, c2);
result.set(j+1, c1);
}
}
}
updateTable();
}
});
orderbycost.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v) {
int i,j;
for(i=0;i<result.size();i++)
{
for(j=0;j<result.size()-1;j++)
{
Car c1=result.get(j);
Car c2=result.get(j+1);
if(c1.cost<c2.cost)
{
result.set(j, c2);
result.set(j+1, c1);
}
}
}
updateTable();
}
});
}
public void updateTable()
{
resultLayout.removeAllViews();
makeTable();
int i;
for(i=0;i<result.size();i++)
{
Car c=result.get(i);
TableRow r=new TableRow(this);
resultLayout.addView(r);
TextView t1,t2,t3;
t1=new TextView(this);
t1.setText(c.name);
t2=new TextView(this);
t2.setText(c.brand);
t3=new TextView(this);
t3.setText(""+c.cost);
r.addView(t1);
r.addView(t2);
r.addView(t3);
ImageView delimage=new ImageView(this);
r.addView(delimage);
delimage.setId(i);
delimage.setImageResource(R.drawable.delete);
delimage.setClickable(true);
delimage.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v) {
String cardetails="Name: "+
result.get(v.getId()).name+
" Brand: "+
result.get(v.getId()).brand+
" Cost: "+
result.get(v.getId()).cost;
Log.d("TEST","Delete Car is "+cardetails);
}
});
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mainLayout=new LinearLayout(this);
setContentView(mainLayout);
mainLayout.setOrientation(LinearLayout.VERTICAL);
db=new Database(this, "cars.db", null, 2);
makeInputs();
makeButtons();
makeJSON();
makeTable();
}
}
public class Database extends SQLiteOpenHelper{
private Context mcontext;
private SQLiteDatabase database;
public Database(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
mcontext=context;
database=this.getWritableDatabase();
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table autos(name text,brand text,cost double)");
}
public ArrayList<Car> getResults()
{
ArrayList<Car> x=new ArrayList<Car>();
Cursor cursor=database.rawQuery("select * from autos",null);
if(cursor.getCount()==0)
{
cursor.close();
return null;
}
int nameindex=cursor.getColumnIndex("name");
int brandindex=cursor.getColumnIndex("brand");
int costindex=cursor.getColumnIndex("cost");
cursor.moveToFirst();
do
{
Car c;
c=new Car(cursor.getString(nameindex),
cursor.getString(brandindex),
cursor.getDouble(costindex));
x.add(c);
}while(cursor.moveToNext());
cursor.close();
return x;
}
public void insert(String name,String brand,double cost)
{
database.execSQL("insert into autos(name,brand,cost) values('"+
name+"','"+brand+"',"+cost+")");
}
public void clearData()
{
database.execSQL("delete from autos");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("drop table autos");
onCreate(db);
}
}
【问题讨论】：
-
尝试深入了解与您的问题相关的代码区域。如果用户不必解析整个类，您将获得更多答案！
-
您没有任何代码可以从表中删除一行！
-
是的，我的问题是代码，我试过了，但最终当我在我的平板电脑上运行应用程序时，当我按下删除按钮时它崩溃并关闭......你能建议使用什么代码吗？从表中删除一行？