基本上当我运行应用程序时，它会崩溃，这是我的代码，我不明白我做错了什么。我知道这与＆＃34;答案＆＃34;有关。变量
sqlAnswer = (EditText)findViewById(R.id.ans1);
这是我的MainActivity代码：我也拿出了答案，因为它出现了一个错误，我认为这是因为进行计算的按钮没有给出相同的输出，而且＃＆＃ 39;基本上是从XML重命名TextView。
public class MainActivity extends Activity implements OnClickListener {
Button sqlUpdate, sqlView;
EditText sqlNumber1, sqlNumber2, sqlAnswer;
@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
sqlUpdate = (Button) findViewById(R.id.bSQLUpdate);
sqlNumber1 = (EditText)findViewById(R.id.num1input);
sqlNumber2 = (EditText)findViewById(R.id.num2input);
sqlAnswer = (EditText)findViewById(R.id.ans1);
sqlView = (Button) findViewById(R.id.bSQLopenView);
sqlView.setOnClickListener(this);
sqlUpdate.setOnClickListener(this);
}
public void onClick(View arg0) {
switch (arg0.getId()){
case R.id.bSQLUpdate:
boolean didItWork = true;
try{
String number_one = sqlNumber1.getText().toString();
String number_two = sqlNumber2.getText().toString();
String answer = sqlAnswer.getText().toString();
DBA entry = new DBA(MainActivity.this);
entry.open();
entry.createEntry(number_one, number_two);
entry.close();
} catch (Exception e) {
e.printStackTrace();
didItWork = false;
}finally{
if (didItWork){
Dialog d = new Dialog(this);
d.setTitle("It Worked");
TextView tv = new TextView(this);
tv.setText("Success!");
d.setContentView(tv);
d.show();
}
}
break;
case R.id.bSQLopenView:
Intent i = new Intent("com.cmpcione.calculator.SQLVIEW");
startActivity(i);
break;
}
}
public void sum(View v) {
EditText number1input = (EditText)findViewById(R.id.num1input);
EditText number2input = (EditText)findViewById(R.id.num2input);
Integer num1=Integer.parseInt(number1input.getText().toString()),num2=Integer.parseInt(number2input.getText().toString());
Integer ans1=num1+num2;
TextView answer=(TextView)findViewById(R.id.ans1);
answer.setText(ans1.toString());
}
DBA类的代码：
public class DBA {
public static final String KEY_ROWID = "_id";
public static final String KEY_NUMBER1 = "num1input";
public static final String KEY_NUMBER2 = "num2input";
public static final String KEY_ANSWER = "ans1";
private static final String DATABASE_NAME = "CalculationsDB";
private static final String DATABASE_TABLE = "Calculation_table";
private static final int DATABASE_VERSION = 2;
private DbHelper ourHelper;
private final Context ourContext;
private SQLiteDatabase ourDatabase;
private static class DbHelper extends SQLiteOpenHelper{
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
//creates table and rows
db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" +
KEY_ROWID + " INTEGER PRIMARY KEY, " +
KEY_NUMBER1 + " TEXT NOT NULL, " +
KEY_NUMBER2 + " TEXT NOT NULL, " +
KEY_ANSWER + " TEXT NOT NULL);"
);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
}
public DBA(Context c){
ourContext = c;
}
public DBA open() {
ourHelper = new DbHelper(ourContext);
ourDatabase = ourHelper.getWritableDatabase();
return this;
}
public void close() {
ourHelper.close();
}
public long createEntry(String number_one, String number_two) {
// TODO Auto-generated method stub
ContentValues cv = new ContentValues();
cv.put(KEY_NUMBER1, number_one);
cv.put(KEY_NUMBER2, number_two);
cv.put(KEY_ANSWER, answer);
return ourDatabase.insert(DATABASE_TABLE, null, cv);
}
public String getData() {
// TODO Auto-generated method stub
String[] columns = new String[]{KEY_ROWID, KEY_NUMBER1, KEY_NUMBER2};
//using the cursor to read from database
Cursor c = ourDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);
String result = " ";
int iRow = c.getColumnIndex(KEY_ROWID);
int iNumber1 = c.getColumnIndex(KEY_NUMBER1);
int iNumber2 = c.getColumnIndex(KEY_NUMBER2);
int iAnswer = c.getColumnIndex(KEY_ANSWER);
for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
//it gets the string of our index then it gets the first number and then the last
result = result + c.getString(iRow) + " " + c.getString(iNumber1) + " " + c.getString(iNumber2) + "\n";
}
return null;
}
}
activity_main.xml如下，我在这里有几个按钮，你可以看到：
<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.cmpcione.calculator.MainActivity$PlaceholderFragment" >
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:orientation="vertical" >
<TextView
android:id="@+id/num1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/num1" />
<EditText
android:id="@+id/num1input"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10" >
</EditText>
<TextView
android:id="@+id/num2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/num2" />
<EditText
android:id="@+id/num2input"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10" />
<Button
android:id="@+id/calc_sum"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="sum"
android:text="@string/calc_sum" />
<Button
android:id="@+id/calc_sub"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="substract"
android:text="@string/calc_sub" />
<Button
android:id="@+id/calc_mul"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="multiply"
android:text="@string/calc_mul" />
<Button
android:id="@+id/calc_div"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="divide"
android:text="@string/calc_div" />
<TextView
android:id="@+id/ans2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingBottom="5dp"
android:text="@string/answer" />
<Button
android:id="@+id/bSQLUpdate"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Update Database" />
<Button
android:id="@+id/bSQLopenView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="View Database" />
</LinearLayout>
<TextView
android:id="@+id/ans1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/linearLayout1"
android:layout_marginBottom="132dp"
android:layout_marginLeft="139dp"
android:text="@string/ans" />
</RelativeLayout>
logcat的完整列表：它从无法将数字插入数据库开始：
04-11 17:57:48.177: E/AndroidRuntime(278): FATAL EXCEPTION: main
04-11 17:57:48.177: E/AndroidRuntime(278): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cmpcione.calculator/com.cmpcione.calculator.MainActivity}: java.lang.ClassCastException: android.widget.TextView
04-11 17:57:48.177: E/AndroidRuntime(278): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
04-11 17:57:48.177: E/AndroidRuntime(278): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
04-11 17:57:48.177: E/AndroidRuntime(278): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
04-11 17:57:48.177: E/AndroidRuntime(278): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
04-11 17:57:48.177: E/AndroidRuntime(278): at android.os.Handler.dispatchMessage(Handler.java:99)
04-11 17:57:48.177: E/AndroidRuntime(278): at android.os.Looper.loop(Looper.java:123)
04-11 17:57:48.177: E/AndroidRuntime(278): at android.app.ActivityThread.main(ActivityThread.java:4627)
04-11 17:57:48.177: E/AndroidRuntime(278): at java.lang.reflect.Method.invokeNative(Native Method)
04-11 17:57:48.177: E/AndroidRuntime(278): at java.lang.reflect.Method.invoke(Method.java:521)
04-11 17:57:48.177: E/AndroidRuntime(278): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
04-11 17:57:48.177: E/AndroidRuntime(278): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
04-11 17:57:48.177: E/AndroidRuntime(278): at dalvik.system.NativeStart.main(Native Method)
04-11 17:57:48.177: E/AndroidRuntime(278): Caused by: java.lang.ClassCastException: android.widget.TextView
04-11 17:57:48.177: E/AndroidRuntime(278): at com.cmpcione.calculator.MainActivity.onCreate(MainActivity.java:27)
04-11 17:57:48.177: E/AndroidRuntime(278): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
04-11 17:57:48.177: E/AndroidRuntime(278): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
答案 0 :(得分：1)
ans1是TextView
<TextView
android:id="@+id/ans1"
所以改变这个
sqlAnswer = (EditText)findViewById(R.id.ans1);
要
TextView sqlAnswer =(TextView)findViewById(R.id.ans1);