利用SQLite和SharedPreferences制作一个简易app(Android Studio),写出Java和Layout代码
时间: 2024-03-01 22:55:48 浏览: 32
好的,下面给出Java和Layout代码,实现一个简单的记录备忘录的app。
MainActivity.java:
```java
import androidx.appcompat.app.AppCompatActivity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private EditText editText;
private ListView listView;
private List<String> dataList = new ArrayList<>();
private ArrayAdapter<String> adapter;
private SQLiteDatabase db;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText = findViewById(R.id.edit_text);
listView = findViewById(R.id.list_view);
adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, dataList);
listView.setAdapter(adapter);
MemoDbHelper dbHelper = new MemoDbHelper(this, "Memo.db", null, 1);
db = dbHelper.getWritableDatabase();
Cursor cursor = db.query("memo", null, null, null, null, null, null);
if (cursor.moveToFirst()) {
do {
String content = cursor.getString(cursor.getColumnIndex("content"));
dataList.add(content);
} while (cursor.moveToNext());
adapter.notifyDataSetChanged();
}
cursor.close();
}
public void addMemo(View view) {
String content = editText.getText().toString();
if (content.isEmpty()) {
Toast.makeText(this, "请输入备忘录内容", Toast.LENGTH_SHORT).show();
return;
}
ContentValues values = new ContentValues();
values.put("content", content);
db.insert("memo", null, values);
dataList.add(content);
adapter.notifyDataSetChanged();
editText.setText("");
}
@Override
protected void onDestroy() {
super.onDestroy();
db.close();
}
}
```
MemoDbHelper.java:
```java
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class MemoDbHelper extends SQLiteOpenHelper {
public static final String CREATE_MEMO = "create table memo("
+ "id integer primary key autoincrement, "
+ "content text)";
public MemoDbHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_MEMO);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
```
activity_main.xml:
```xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="16dp">
<EditText
android:id="@+id/edit_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="请输入备忘录内容" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end"
android:text="添加"
android:onClick="addMemo" />
<ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="16dp"/>
</LinearLayout>
```
注意:上述代码只是一个简单的示例,没有对输入内容做长度限制、输入合法性检查等操作。完整的实际应用需要更加完善的代码。