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Android helper class for showing cheat sheets (tooltips) for icon-only UI elements on long-press. This is already default platform behavior for icon-only action bar items and tabs. This class provides this behavior for any other such UI element.
/*
* Copyright 2012 Roman Nurik
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.cheatsheet;
import android.content.Context;
import android.graphics.Rect;
import android.text.TextUtils;
import android.view.Gravity;
import android.view.View;
import android.widget.Toast;
/**
* Helper class for showing cheat sheets (tooltips) for icon-only UI elements on long-press. This is
* already default platform behavior for icon-only {@link android.app.ActionBar} items and tabs.
* This class provides this behavior for any other such UI element.
*
* <p>Based on the original action bar implementation in <a href="https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/core/java/com/android/internal/view/menu/ActionMenuItemView.java">
* ActionMenuItemView.java</a>.
*/
public class CheatSheet {
/**
* The estimated height of a toast, in dips (density-independent pixels). This is used to
* determine whether or not the toast should appear above or below the UI element.
*/
private static final int ESTIMATED_TOAST_HEIGHT_DIPS = 48;
/**
* Sets up a cheat sheet (tooltip) for the given view by setting its {@link
* android.view.View.OnLongClickListener}. When the view is long-pressed, a {@link Toast} with
* the view's {@link android.view.View#getContentDescription() content description} will be
* shown either above (default) or below the view (if there isn't room above it).
*
* @param view The view to add a cheat sheet for.
*/
public static void setup(View view) {
view.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View view) {
return showCheatSheet(view, view.getContentDescription());
}
});
}
/**
* Sets up a cheat sheet (tooltip) for the given view by setting its {@link
* android.view.View.OnLongClickListener}. When the view is long-pressed, a {@link Toast} with
* the given text will be shown either above (default) or below the view (if there isn't room
* above it).
*
* @param view The view to add a cheat sheet for.
* @param textResId The string resource containing the text to show on long-press.
*/
public static void setup(View view, final int textResId) {
view.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View view) {
return showCheatSheet(view, view.getContext().getString(textResId));
}
});
}
/**
* Sets up a cheat sheet (tooltip) for the given view by setting its {@link
* android.view.View.OnLongClickListener}. When the view is long-pressed, a {@link Toast} with
* the given text will be shown either above (default) or below the view (if there isn't room
* above it).
*
* @param view The view to add a cheat sheet for.
* @param text The text to show on long-press.
*/
public static void setup(View view, final CharSequence text) {
view.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View view) {
return showCheatSheet(view, text);
}
});
}
/**
* Removes the cheat sheet for the given view by removing the view's {@link
* android.view.View.OnLongClickListener}.
*
* @param view The view whose cheat sheet should be removed.
*/
public static void remove(final View view) {
view.setOnLongClickListener(null);
}
/**
* Internal helper method to show the cheat sheet toast.
*/
private static boolean showCheatSheet(View view, CharSequence text) {
if (TextUtils.isEmpty(text)) {
return false;
}
final int[] screenPos = new int[2]; // origin is device display
final Rect displayFrame = new Rect(); // includes decorations (e.g. status bar)
view.getLocationOnScreen(screenPos);
view.getWindowVisibleDisplayFrame(displayFrame);
final Context context = view.getContext();
final int viewWidth = view.getWidth();
final int viewHeight = view.getHeight();
final int viewCenterX = screenPos[0] + viewWidth / 2;
final int screenWidth = context.getResources().getDisplayMetrics().widthPixels;
final int estimatedToastHeight = (int) (ESTIMATED_TOAST_HEIGHT_DIPS
* context.getResources().getDisplayMetrics().density);
Toast cheatSheet = Toast.makeText(context, text, Toast.LENGTH_SHORT);
boolean showBelow = screenPos[1] < estimatedToastHeight;
if (showBelow) {
// Show below
// Offsets are after decorations (e.g. status bar) are factored in
cheatSheet.setGravity(Gravity.TOP | Gravity.CENTER_HORIZONTAL,
viewCenterX - screenWidth / 2,
screenPos[1] - displayFrame.top + viewHeight);
} else {
// Show above
// Offsets are after decorations (e.g. status bar) are factored in
cheatSheet.setGravity(Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL,
viewCenterX - screenWidth / 2,
displayFrame.bottom - screenPos[1]);
}
cheatSheet.show();
return true;
}
}
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