I am developing a small app where users can post something and comment on a post. I am using the Instamaterial project on github as a reference.
There is a comment activity with animation while users post a new comment. Everything is working cool ... but when I post the very first comment... the app is crashing and not showing the comment animation (scroll to top) I spent the whole day trying ... but could not find the solution.
public class CommentsActivity extends AppCompatActivity implements SendCommentButton.OnSendClickListener {
public static final String ARG_DRAWING_START_LOCATION = "arg_drawing_start_location";
LinearLayout contentRoot;
RecyclerView rvComments;
LinearLayout llAddComment;
EditText etComment;
SendCommentButton btnSendComment;
private CommentsAdapter commentsAdapter;
private int drawingStartLocation;
Toolbar toolbar;
private int currentPostID;
DatabaseHelper db;
private PreferencesManager preferencesManager;
ArrayList<PostResponse.PostComments> comments;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_comments);
toolbar = (Toolbar) findViewById(R.id.toolbar);
contentRoot = (LinearLayout) findViewById(R.id.contentRoot);
rvComments = (RecyclerView) findViewById(R.id.rvComments);
llAddComment = (LinearLayout) findViewById(R.id.llAddComment);
etComment = (EditText) findViewById(R.id.etComment);
btnSendComment = (SendCommentButton) findViewById(R.id.btnSendComment);
preferencesManager = new PreferencesManager(CommentsActivity.this);
db = new DatabaseHelper(CommentsActivity.this);
setupToolbar();
setupComments();
setupSendCommentButton();
drawingStartLocation = getIntent().getIntExtra(ARG_DRAWING_START_LOCATION, 0);
if (savedInstanceState == null) {
contentRoot.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
contentRoot.getViewTreeObserver().removeOnPreDrawListener(this);
startIntroAnimation();
return true;
}
});
}
}
protected void setupToolbar() {
if (toolbar != null) {
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayShow
HomeEnabled(true);
toolbar.setNavigationIcon(R.mipmap.ic_menu_cancel);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
onBackPressed();
}
});
}
}
private void setupComments() {
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
rvComments.setLayoutManager(linearLayoutManager);
rvComments.setHasFixedSize(true);
currentPostID = getIntent().getIntExtra(PostResponse.KEY_ID, -1);
comments = db.getCommentsByPostID(currentPostID);
commentsAdapter = new CommentsAdapter(this, comments);
rvComments.setAdapter(commentsAdapter);
rvComments.setOverScrollMode(View.OVER_SCROLL_NEVER);
rvComments.setOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
if (newState == RecyclerView.SCROLL_STATE_DRAGGING) {
commentsAdapter.setAnimationsLocked(true);
}
}
});
}
private void setupSendCommentButton() {
btnSendComment.setOnSendClickListener(this);
}
private void startIntroAnimation() {
ViewCompat.setElevation(getToolbar(), 0);
contentRoot.setScaleY(0.1f);
contentRoot.setPivotY(drawingStartLocation);
llAddComment.setTranslationY(200);
contentRoot.animate()
.scaleY(1)
.setDuration(200)
.setInterpolator(new AccelerateInterpolator())
.setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
ViewCompat.setElevation(getToolbar(), Utils.dpToPx(8));
animateContent();
}
})
.start();
}
private void animateContent() {
commentsAdapter.updateItems();
llAddComment.animate().translationY(0)
.setInterpolator(new DecelerateInterpolator())
.setDuration(200)
.start();
}
@Override
public void onBackPressed() {
ViewCompat.setElevation(getToolbar(), 0);
contentRoot.postDelayed(new Runnable() {
@Override
public void run() {
contentRoot.animate()
.translationY(Utils.getScreenHeight(CommentsActivity.this))
.setDuration(200)
.setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
CommentsActivity.super.onBackPressed();
overridePendingTransition(0, 0);
}
})
.start();
}
}, 100);
}
@Override
public void onSendClickListener(View v) {
if (validateComment()) {
publishComment(etComment.getText().toString());
PostResponse.PostComments newComment = new PostResponse().new PostComments();
newComment.user_id = Integer.parseInt(preferencesManager.getUserID());
newComment.comment = etComment.getText().toString();
newComment.post_id = currentPostID;
commentsAdapter.addItem(newComment);
commentsAdapter.setAnimationsLocked(false);
commentsAdapter.setDelayEnterAnimation(true);
rvComments.smoothScrollBy(0, rvComments.getChildAt(0).getHeight() * commentsAdapter.getItemCount());
etComment.setText(null);
btnSendComment.setCurrentState(SendCommentButton.STATE_DONE);
}
}
private boolean validateComment() {
if (TextUtils.isEmpty(etComment.getText())) {
btnSendComment.startAnimation(AnimationUtils.loadAnimation(this, R.anim.shake_error));
return false;
}
return true;
}
private Toolbar getToolbar(){
return toolbar;
}
/************************************************
* VOLLEY CALLS TO PUBLISH A COMMENT
* *****************************************************/
private void publishComment(final String comment) {
//Code here
}
}
This is my adapter
public class CommentsAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private Context context;
private int lastAnimatedPosition = -1;
private int avatarSize;
private int itemsCount = 0;
private boolean animationsLocked = false;
private boolean delayEnterAnimation = true;
List<PostResponse.PostComments> mItems;
public CommentsAdapter(Context context, List<PostResponse.PostComments> mItems) {
this.context = context;
this.mItems = mItems;
avatarSize = context.getResources().getDimensionPixelSize(R.dimen.comment_avatar_size);
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
final View view = LayoutInflater.from(context).inflate(R.layout.item_comment, parent, false);
return new CommentViewHolder(view);
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
runEnterAnimation(viewHolder.itemView, position);
CommentViewHolder holder = (CommentViewHolder) viewHolder;
holder.tvComment.setText(mItems.get(position).comment);
Picasso.with(context)
.load(R.drawable.user_profile)
.centerCrop()
.resize(avatarSize, avatarSize)
.transform(new RoundedTransformation())
.into(holder.ivUserAvatar);
}
private void runEnterAnimation(View view, int position) {
if (animationsLocked) return;
if (position > lastAnimatedPosition) {
lastAnimatedPosition = position;
view.setTranslationY(100);
view.setAlpha(0.f);
view.animate()
.translationY(0).alpha(1.f)
.setStartDelay(delayEnterAnimation ? 20 * (position) : 0)
.setInterpolator(new DecelerateInterpolator(2.f))
.setDuration(300)
.setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
animationsLocked = true;
}
})
.start();
}
}
@Override
public int getItemCount() {
return mItems.size();
}
public void updateItems() {
notifyDataSetChanged();
}
public void addItem(PostResponse.PostComments newComment) {
mItems.add(newComment);
notifyItemInserted(mItems.size() - 1);
}
public void setAnimationsLocked(boolean animationsLocked) {
this.animationsLocked = animationsLocked;
}
public void setDelayEnterAnimation(boolean delayEnterAnimation) {
this.delayEnterAnimation = delayEnterAnimation;
}
public static class CommentViewHolder extends RecyclerView.ViewHolder {
@Bind(R.id.ivUserAvatar)
ImageView ivUserAvatar;
@Bind(R.id.tvComment)
TextView tvComment;
public CommentViewHolder(View view) {
super(view);
ButterKnife.bind(this, view);
}
}
}
Here is the screens.
Working Well
The first works well but adding the first comment never works. I get this exception.
// Here is the exception
java.lang.NullPointerException
at com.test.abc.CommentsActivity.onSendClickListener(CommentsActivity.java:214)
at com.test.abc.views.SendCommentButton.onClick(SendCommentButton.java:80)
at android.view.View.performClick(View.java:4463)
at android.view.View$PerformClick.run(View.java:18770)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:193)