替代答案
以下是一个非常基本但有效的示例的代码。然而，它更进一步，结合了ListView并允许通过长按项目中的删除ListView.
但是，这不使用片段。
有3段代码，主要活动 (MainActivity.java), SQLiteOpenHelper 子类犯罪数据库助手 (CrimeDBHelper.java）和 MainActivity 的布局，activity_main.xml:-
活动主文件
这非常简单。请注意，它包括一个ListView在最后。
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="The Crime Thing"
android:layout_gravity="center"
android:textStyle="bold"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="wrap_content"
android:text="Crime Title"
/>
<EditText
android:id="@+id/crimetitle"
android:layout_width="0dp"
android:layout_weight="3"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="wrap_content"
android:text="Crime Date"
/>
<EditText
android:id="@+id/crimedate"
android:layout_width="0dp"
android:layout_weight="3"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="wrap_content"
android:text="Suspect"
/>
<EditText
android:id="@+id/crimesuspect"
android:layout_width="0dp"
android:layout_weight="3"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="wrap_content"
android:text="Crime Solved?"
/>
<CheckBox
android:id="@+id/crimesolved"
android:layout_width="0dp"
android:layout_weight="3"
android:layout_height="wrap_content" />
</LinearLayout>
<Button
android:id="@+id/addcrime"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="ADD CRIME"/>
<Button
android:id="@+id/dltcrime"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="DLT CRIME (ID=?)"/>
<ListView
android:id="@+id/crimelist"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</ListView>
CrimeDBHelper.java
除了附加方法之外，大多数都是相似的getCrimeList()，这将返回一个 Cursor，其中包含犯罪表中的所有数据（用于填充 ListView）。
public class CrimeDBHelper extends SQLiteOpenHelper {
public static final String DBNAME = "crimesdb";
public static final int DBVERSION = 1;
public static final String CRIMESTABLE = "crimes";
public static final String CRIMEID_COL = "_id";
public static final String CRIMETITLE_COL = "crimetitle";
public static final String CRIMEDATE_COL = "crimedate";
public static final String CRIMESUSPECT_COL = "crimesuspect";
public static final String CRIMESOLVED_COL = "crimesolved";
public static final String TABLECRTSQL =
"CREATE TABLE " + CRIMESTABLE + "(" +
CRIMEID_COL + " INTEGER PRIMARY KEY," +
CRIMETITLE_COL + " TEXT," +
CRIMEDATE_COL + " TEXT, " +
CRIMESUSPECT_COL + " TEXT, " +
CRIMESOLVED_COL + " INTEGER" +
");";
public CrimeDBHelper(Context context) {
super(context, DBNAME, null, DBVERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(TABLECRTSQL);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldversion, int newversion) {
}
public long addCrime(String crimetitle, String crimedate, String crimesuspect, int crimesolved) {
SQLiteDatabase db = getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(CRIMETITLE_COL,crimetitle);
cv.put(CRIMEDATE_COL,crimedate);
cv.put(CRIMESUSPECT_COL,crimesuspect);
cv.put(CRIMESOLVED_COL,crimesolved);
return db.insert(CRIMESTABLE,null,cv);
}
public int deleteCrime(long crimeid) {
SQLiteDatabase db = getWritableDatabase();
String whereclause = CRIMEID_COL + "=?";
String[] whereargs = {Long.toString(crimeid)};
return db.delete(CRIMESTABLE,whereclause,whereargs);
}
public Cursor getCrimeList() {
SQLiteDatabase db = getWritableDatabase();
return db.query(CRIMESTABLE,null,null,null,null,null,null,null);
}
}
MainActivity.java
public class MainActivity extends AppCompatActivity {
EditText mCrimeTitle;
EditText mCrimeDate;
EditText mCrimeSuspect;
CheckBox mCrimeSolved;
Button mAddCrime;
Button mDltCrime;
ListView mCrimeList;
CrimeDBHelper dbhlpr = new CrimeDBHelper(this);
Cursor crimelist;
SimpleCursorAdapter sca;
long lastcrimeid;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mCrimeTitle = (EditText) findViewById(R.id.crimetitle);
mCrimeDate = (EditText) findViewById(R.id.crimedate);
mCrimeSuspect = (EditText) findViewById(R.id.crimesuspect);
mCrimeSolved = (CheckBox) findViewById(R.id.crimesolved);
mCrimeList = (ListView) findViewById(R.id.crimelist);
mAddCrime = (Button) findViewById(R.id.addcrime);
mDltCrime = (Button) findViewById(R.id.dltcrime);
crimelist = dbhlpr.getCrimeList();
// Setup Button to Add a crime
mAddCrime.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
int solved = 0;
if (mCrimeSolved.isChecked()) {
solved = 1;
}
lastcrimeid = dbhlpr.addCrime(
mCrimeTitle.getText().toString(),
mCrimeDate.getText().toString(),
mCrimeSuspect.getText().toString(),
solved
);
mDltCrime.setText("DLT CRIME (ID=" + Long.toString(lastcrimeid) + ")");
mDltCrime.setTag(lastcrimeid);
crimelist = dbhlpr.getCrimeList();
sca.swapCursor(crimelist);
}
});
// Setup button to delete the latest Crime added
mDltCrime.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
//dbhlpr.deleteCrime(lastcrimeid); can do it this way
if (view.getTag() != null) {
dbhlpr.deleteCrime((long)view.getTag());
crimelist = dbhlpr.getCrimeList();
sca.swapCursor(crimelist);
}
}
});
sca = new SimpleCursorAdapter(this,
android.R.layout.simple_list_item_1,
crimelist,
new String[]{CrimeDBHelper.CRIMETITLE_COL},
new int[]{android.R.id.text1},
0
);
mCrimeList.setAdapter(sca);
mCrimeList.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
dbhlpr.deleteCrime(l);
crimelist = dbhlpr.getCrimeList();
sca.swapCursor(crimelist);
return true;
}
});
}
protected void onDestroy() {
super.onDestroy();
if (crimelist != null) {
crimelist.close();
}
}
}
首先要注意的是这条线long lastcrimeid;，这是在类级别声明的，因此在整个过程中非常可用（你遇到的问题long databaseID
