GIF OF ACTIVITY ＆lt; --------
我想要做的只是从 RecyclerView适配器显示我的 SQLite数据，一些部分的工作原理，但不具体。 如果您有任何反馈，请不要犹豫，放纵我！
见下相关代码：
MachineCreation.java
public class MachineCreation extends AppCompatActivity {
private EditText etName, etLocation;
private Button mButton;
private DBHelpter mDBHelpter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_machine_creation);
mDBHelpter = new DBHelpter(this);
etName = (EditText) findViewById(R.id.etName);
etLocation = (EditText) findViewById(R.id.etLocation);
mButton = (Button) findViewById(R.id.button);
mButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String name = String.valueOf(etName.getText());
String location = String.valueOf(etLocation.getText());
mDBHelpter.insertNewMachine(name, location);
Intent intent = new Intent(MachineCreation.this, MainActivity.class);
startActivity(intent);
}
});
}
machines_list.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:text="CALDAS"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/tvLocation"
android:layout_centerVertical="true"
android:textSize="36sp"
android:paddingTop="10dp"
android:paddingBottom="10dp"
android:paddingLeft="5dp"/>
<TextView
android:text="$ 0.0"
android:textSize="36sp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:id="@+id/tvMoney"
android:paddingRight="5dp"
android:paddingBottom="10dp"
android:paddingTop="10dp"/>
MainActivity
public class MainActivity extends AppCompatActivity {
private DBHelpter mDBHelpter;
private RecyclerView mRecyclerView;
private ArrayList<MachinesClass> mList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mDBHelpter = new DBHelpter(this);
mRecyclerView = (RecyclerView) findViewById(R.id.rvNew);
mRecyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setAdapter(new MachinesAdapter(getApplicationContext(), mList));
}
activity_main.xml中
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="tech.destinum.machines.MainActivity"
android:layout_marginTop="@dimen/activity_vertical_margin"
android:layout_marginBottom="@dimen/activity_vertical_margin"
android:layout_marginLeft="@dimen/activity_horizontal_margin"
android:layout_marginRight="@dimen/activity_horizontal_margin">
<android.support.design.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.FloatingActionButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:clickable="true"
app:fabSize="mini"
app:srcCompat="@mipmap/ic_add_black_24dp"
android:id="@+id/floatingActionButton"
android:layout_gravity="bottom|right"/>
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/rvNew"/>
</android.support.design.widget.CoordinatorLayout>
DBHelper
public class DBHelpter extends SQLiteOpenHelper {
private static final String DB_NAME = "machines.db";
private static final int DB_VERSION = 1;
public static final String TABLE_MACHINES = "machines";
public static final String MACHINES_COLUMN_NAME = "name";
public static final String MACHINES_COLUMN_LOCATION = "location";
public static final String MACHINES_ID = "id";
public static final String TABLE_INCOME = "income";
public static final String INCOME_COLUMN_MONEY = "money";
public static final String INCOME_COLUMN_DATE = "date";
public static final String INCOME_COLUMN_NOTE = "note";
public static final String INCOME_ID = "id";
public DBHelpter(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String query1 = String.format("CREATE TABLE " + TABLE_MACHINES + "("
+ MACHINES_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ MACHINES_COLUMN_NAME + " TEXT NOT NULL, "
+ MACHINES_COLUMN_LOCATION + " TEXT NOT NULL)",
TABLE_MACHINES, MACHINES_COLUMN_NAME, MACHINES_COLUMN_LOCATION, MACHINES_ID);
String query2 = String.format("CREATE TABLE " + TABLE_INCOME + "("
+ INCOME_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ INCOME_COLUMN_MONEY + " REAL NOT NULL, "
+ INCOME_COLUMN_DATE + " DATE NOT NULL, "
+ INCOME_COLUMN_NOTE + " TEXT NOT NULL)",
TABLE_INCOME, INCOME_ID, INCOME_COLUMN_MONEY, INCOME_COLUMN_DATE, INCOME_COLUMN_NOTE);
db.execSQL(query1);
db.execSQL(query2);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
String query1 = String.format("DROP TABLE IF EXISTS " + TABLE_MACHINES);
String query2 = String.format("DROP TABLE IF EXISTS " + TABLE_INCOME);
db.execSQL(query1);
db.execSQL(query2);
onCreate(db);
}
public void insertNewMachine(String name, String location){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(MACHINES_COLUMN_NAME, name);
values.put(MACHINES_COLUMN_LOCATION, location);
db.insertWithOnConflict(TABLE_MACHINES, null, values, SQLiteDatabase.CONFLICT_REPLACE);
db.close();
}
public void updateMachine(long id, String name, String location){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(MACHINES_COLUMN_NAME, name);
values.put(MACHINES_COLUMN_LOCATION, location);
db.update(TABLE_MACHINES, values, "id = ?", new String[]{Long.toString(id)});
db.close();
}
public void deleteMachine(long id){
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_MACHINES, "id = ?", new String[]{id + ""});
db.close();
}
public ArrayList<MachinesClass> getAllMachines(){
ArrayList<MachinesClass> machinesList = new ArrayList<>();
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM "+ TABLE_MACHINES, null);
while (cursor.moveToNext()){
final long id = cursor.getLong(cursor.getColumnIndex(MACHINES_ID));
final String name = cursor.getString(cursor.getColumnIndex(MACHINES_COLUMN_NAME));
final String location = cursor.getString(cursor.getColumnIndex(MACHINES_COLUMN_LOCATION));
machinesList.add(new MachinesClass(id, name, location));
}
cursor.close();
db.close();
return machinesList;
}
}
MachinesClass.java
public class MachinesClass {
public long id;
public String name, location;
public MachinesClass(long id, String name, String location) {
this.id = id;
this.name = name;
this.location = location;
}
}
MachinesAdapter.java
public class MachinesAdapter extends RecyclerView.Adapter<MachinesAdapter.ViewHolder> {
private ArrayList<MachinesClass> machinesList = new ArrayList<MachinesClass>();
private LayoutInflater mInflater;
public MachinesAdapter(Context context, ArrayList<MachinesClass> machinesList){
this.mInflater = LayoutInflater.from(context);
this.machinesList = machinesList;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.machines_list, parent, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
MachinesClass item = machinesList.get(position);
holder.mLocation.setText(item.location);
notifyDataSetChanged();
}
@Override
public int getItemCount() {
return machinesList != null ? machinesList.size() : 0;
}
public static class ViewHolder extends RecyclerView.ViewHolder{
public TextView mLocation, mMoney;
public ViewHolder(View itemView) {
super(itemView);
mLocation = (TextView) itemView.findViewById(R.id.tvLocation);
mMoney = (TextView) itemView.findViewById(R.id.tvMoney);
}
}
}
当我在 MainActivity.java 中更改行：
mRecyclerView.setAdapter(new MachinesAdapter(getApplicationContext(), mList)); 到
mRecyclerView.setAdapter(new MachinesAdapter(getApplicationContext(), mList =
mDBHelpter.getAllMachines())); 我接下来的错误。
我知道我必须打电话给 DBHelper 才能获得所有机器，但我不知道怎么做正确。
错误
FATAL EXCEPTION: main
Process: tech.destinum.machines, PID: 3604
java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255)
at java.util.ArrayList.get(ArrayList.java:308)
at tech.destinum.machines.MachinesAdapter.onBindViewHolder(MachinesAdapter.java:33)
at tech.destinum.machines.MachinesAdapter.onBindViewHolder(MachinesAdapter.java:14)
at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6279)
at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6312)
at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5258)
at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5521)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5363)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5359)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2141)
at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1525)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1488)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:585)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3506)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3254)
at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3767)
at android.view.View.layout(View.java:16630)
at android.view.ViewGroup.layout(ViewGroup.java:5437)
at android.support.design.widget.CoordinatorLayout.layoutChild(CoordinatorLayout.java:1167)
at android.support.design.widget.CoordinatorLayout.onLayoutChild(CoordinatorLayout.java:852)
at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:871)
at android.view.View.layout(View.java:16630)
at android.view.ViewGroup.layout(ViewGroup.java:5437)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1079)
at android.view.View.layout(View.java:16630)
at android.view.ViewGroup.layout(ViewGroup.java:5437)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
at android.view.View.layout(View.java:16630)
at android.view.ViewGroup.layout(ViewGroup.java:5437)
at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:437)
at android.view.View.layout(View.java:16630)
at android.view.ViewGroup.layout(ViewGroup.java:5437)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
at android.view.View.layout(View.java:16630)
at android.view.ViewGroup.layout(ViewGroup.java:5437)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
at android.view.View.layout(View.java:16630)
at android.view.ViewGroup.layout(ViewGroup.java:5437)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
at com.android.internal.policy.PhoneWindow$DecorView.onLayout(PhoneWindow.java:2678)
at android.view.View.layout(View.java:16630)
at android.view.ViewGroup.layout(ViewGroup.java:5437)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2171)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1931)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
at android.view.Choreographer.doCallbacks(Choreographer.java:670)
at android.view.Choreographer.doFrame(Choreographer.java:606)
at android.
答案 0 :(得分：0)
在onBindViewHolder中，您正在使用machinesList.clear（）清除machinesList;并且重用它我认为是一个错误。
答案 1 :(得分：0)
所以经过一段时间的挖掘，我找到了一个 SOLUTION ，我不得不改变 onBindViewHolder 方法，删除2行。 machinesList.clear 和 notifyDataSetChanged（）。
感谢所有有输入的人！