我有一个recyclerview，可从主机中的数据库获取数据。我想在每个帖子中放置一个按钮，可以将该帖子添加到收藏夹列表（另一个活动中的recyclerview）。我编码这些，但是那行不通，只是告诉我用力接近。事实上，我很困惑这是怎么回事。有人可以帮忙吗？ 这是我的MainActivity代码，其中显示了帖子：
public class MainActivity extends AppCompatActivity {
private RecyclerView recyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setupRecyclerView();
getPostsFromDatabase();
ApiService apiService = new ApiService(this);
apiService.getPosts(new ApiService.OnPostsRecieved() {
@Override
public void onRecieved(List<Post> posts) {
PostDatabseOpenHelper openHelper = new PostDatabseOpenHelper(MainActivity.this);
openHelper.addPosts(posts);
PostAdapter postAdapter = new PostAdapter(MainActivity.this, posts);
recyclerView.setAdapter(postAdapter);
}
});
}
private void setupRecyclerView() {
recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
LinearLayoutManager mLayoutManager = new LinearLayoutManager(this);
mLayoutManager.setReverseLayout(true);
mLayoutManager.setStackFromEnd(true);
recyclerView.setLayoutManager(mLayoutManager);}
private void getPostsFromDatabase() {
PostDatabseOpenHelper databseOpenHelper = new PostDatabseOpenHelper(this);
List<Post> posts = databseOpenHelper.getPosts();
PostAdapter postAdapter = new PostAdapter(this, posts);
recyclerView.setAdapter(postAdapter);
}
}
这是databaseOpenHelper代码：
public class PostDatabseOpenHelper extends SQLiteOpenHelper {
public static final String COL_ID="col_id";
public static final String COL_CONTENT="col_content";
public static final String COL_IS_FAV="col_is_fav";
private static final String SQL_COMMAND_CREATE_POST_TABLE="CREATE TABLE IF NOT EXISTS "+POST_TABLE_NAME+"("+
COL_ID+" INTEGER PRIMARY KEY AUTOINCREMENT, "+
COL_CONTENT+" TEXT,"+
COL_IS_FAV+"INTEGER DEFAULT 0);";
@Override
public void onCreate(SQLiteDatabase db) {
try {
db.execSQL(SQL_COMMAND_CREATE_POST_TABLE);
}catch (SQLException e){
Log.e(TAG, "onCreate: "+e.toString() );
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
public boolean addPost(Post post){
ContentValues cv=new ContentValues();
cv.put(COL_ID,post.getId());
cv.put(COL_CONTENT,post.getContent());
cv.put(COL_IS_FAV,post.getIsFav());
SQLiteDatabase sqLiteDatabase=this.getWritableDatabase();
long isInserted=sqLiteDatabase.insert(POST_TABLE_NAME,null,cv);
Log.i(TAG, "addPost: "+isInserted);
if (isInserted>0){
return true;
}else{
return false;
}
}
public List<Post> getPosts(){
List<Post>posts=new ArrayList<>();
SQLiteDatabase sqliteDatabase =this.getReadableDatabase();
Cursor cursor= sqliteDatabase.rawQuery("SELECT * FROM "+POST_TABLE_NAME,null);
cursor.moveToFirst();
if (cursor.getCount()>0){
while (!cursor.isAfterLast()){
Post post=new Post();
post.setId(cursor.getInt(0));
post.setContent(cursor.getString(1));
post.setIsFav(cursor.getInt(2));
posts.add(post);
cursor.moveToNext();
}
}
cursor.close();
sqliteDatabase.close();
return posts;
}
public void setPostIsFav(int postId,int isFav){
SQLiteDatabase sqliteDatabase=this.getWritableDatabase();
ContentValues contentValues=new ContentValues();
contentValues.put(COL_IS_FAV,isFav);
int rowAffected=sqliteDatabase.update(POST_TABLE_NAME,contentValues,COL_ID+" = ?",new String[]{String.valueOf(postId)});
sqliteDatabase.close();
}
}
这是适配器代码：
public class PostAdapter extends RecyclerView.Adapter<PostAdapter.PostviewHolder> {
private Context context;
private List<Post> posts;
@Override
public PostviewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(context).inflate(R.layout.layout_post,parent,false);
}
@Override
public void onBindViewHolder(@NonNull final PostviewHolder holder, int position) {
final Post post=posts.get(position);
holder.content.setText(post.getContent());
holder.content.setText(posts.get(holder.getAdapterPosition()).getContent());
}
public void btnFavClicked(View view){
PostDatabseOpenHelper helper=new PostDatabseOpenHelper(context);
helper.setPostIsFav(0,1);
}
@Override
public int getItemCount() {
return posts.size();
}
}
这是Favorite.class代码：
public class Favorite extends AppCompatActivity {
private RecyclerView recyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_favorite);
setupRecyclerView();
getPostsFromDatabase();
ApiService apiService = new ApiService(this);
apiService.getPosts(new ApiService.OnPostsRecieved() {
@Override
public void onRecieved(List<Post> posts) {
PostDatabseOpenHelper openHelper = new PostDatabseOpenHelper(Favorite.this);
TextView contentTextView=(TextView)findViewById(R.id.Postcontent);
PostAdapter postAdapter = new PostAdapter(Favorite.this, posts);
recyclerView.setAdapter(postAdapter);}});
}
private void setupRecyclerView() {
recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
LinearLayoutManager mLayoutManager = new LinearLayoutManager(this);
mLayoutManager.setReverseLayout(true);
mLayoutManager.setStackFromEnd(true);
recyclerView.setLayoutManager(mLayoutManager);
}
private void getPostsFromDatabase() {
PostDatabseOpenHelper databseOpenHelper = new PostDatabseOpenHelper(this);
List<Post> posts = databseOpenHelper.getPosts();
PostAdapter postAdapter = new PostAdapter(this, posts);
recyclerView.setAdapter(postAdapter);
}
}
这是崩溃时我的日志：
09-02 14:00:09.617 20392-20392/? E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo: java.lang.IllegalStateException: Couldn't read row 0, col 2 from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2372)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2424)
at android.app.ActivityThread.access$600(ActivityThread.java:169)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1388)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5433)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:924)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:691)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalStateException: Couldn't read row 0, col 2 from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.
at android.database.CursorWindow.nativeGetLong(Native Method)
at android.database.CursorWindow.getLong(CursorWindow.java:507)
at android.database.CursorWindow.getInt(CursorWindow.java:574)
at android.database.AbstractWindowedCursor.getInt(AbstractWindowedCursor.java:69)
at android.app.Activity.performCreate(Activity.java:5179)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1146)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2336)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2424)
at android.app.ActivityThread.access$600(ActivityThread.java:169)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1388)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5433)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)