In xml, you can use ?attr/actionBarSize, but if you need access to that value in Java…
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public int getActionBarSize() { TypedArray styledAttributes = getTheme().obtainStyledAttributes(new int[] { android.R.attr.actionBarSize }); int actionBarSize = (int) styledAttributes.getDimension(0, 0); styledAttributes.recycle(); return actionBarSize; } |
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package com.qozix.view; import android.view.View; import android.view.ViewGroup; import android.view.ViewParent; import java.util.ArrayList; import java.util.Collection; /** * Collection of utility functions for finding Views in a hierarchy. */ public class Finder { /** * Interface with method to determine if a particular View meets arbitrary criteria for inclusion in a * ViewFinder method's result set. */ public interface Qualifier { /** * Qualify boolean. * * @param view the view * @return the boolean */ boolean qualify(View view); } /** * Helper method to pre-cast Views to the type of the declared instance. * * @param <T> The Class reference (View subclass) the View should be cast to. * @param viewGroup The ViewGroup instance to search for the View specified by #id. * @param id The id of the View to be located within this Activity's view tree. * @return The View with the matching id. */ @SuppressWarnings("unchecked") public <T extends View> T findAndCast(ViewGroup viewGroup, int id) { return (T) viewGroup.findViewById(id); } /** * Utility * * @param qualifier * @param view * @return */ private static boolean qualifies(Qualifier qualifier, View view) { return qualifier == null || qualifier.qualify(view); } /** * Utility * * @param view the view * @return view group */ public static ViewGroup getContainingViewGroup(View view) { ViewParent viewParent = view.getParent(); if (viewParent instanceof ViewGroup) { return (ViewGroup) viewParent; } return null; } /** * Find first view. * * @param viewGroup the view group * @param qualifier the qualifier * @return the view */ public static View findFirst(ViewGroup viewGroup, Qualifier qualifier) { for (int i = 0; i < viewGroup.getChildCount(); i++) { View child = viewGroup.getChildAt(i); if (qualifies(qualifier, child)) { return child; } if (child instanceof ViewGroup) { View match = findFirst((ViewGroup) child, qualifier); if (match != null) { return match; } } } return null; } /** * Find all collection. * * @param viewGroup the view group * @return the collection */ public static Collection<View> findAll(ViewGroup viewGroup) { return findAll(viewGroup, null); } /** * Find all collection. * * @param viewGroup the view group * @param qualifier the qualifier * @return the collection */ public static Collection<View> findAll(ViewGroup viewGroup, Qualifier qualifier) { return findAll(viewGroup, qualifier, null); } /** * Find all collection. * * @param viewGroup the view group * @param qualifier the qualifier * @param out the out * @return the collection */ public static Collection<View> findAll(ViewGroup viewGroup, Qualifier qualifier, Collection<View> out) { if (out == null) { out = new ArrayList<>(); } for (int i = 0; i < viewGroup.getChildCount(); i++) { View child = viewGroup.getChildAt(i); if (qualifies(qualifier, child)) { out.add(child); } if (child instanceof ViewGroup) { findAll((ViewGroup) child, qualifier, out); } } return out; } /** * Get first child view. * * @param viewGroup the view group * @return the view */ public static View getFirstChild(ViewGroup viewGroup) { return viewGroup.getChildAt(0); } /** * Get first child view. * * @param viewGroup the view group * @param qualifier the qualifier * @return the view */ public static View getFirstChild(ViewGroup viewGroup, Qualifier qualifier) { for (int i = 0; i < viewGroup.getChildCount(); i++) { View child = viewGroup.getChildAt(i); if (qualifies(qualifier, child)) { return child; } } return null; } /** * Get last child view. * * @param viewGroup the view group * @return the view */ public static View getLastChild(ViewGroup viewGroup) { return viewGroup.getChildAt(viewGroup.getChildCount() - 1); } /** * Get last child view. * * @param viewGroup the view group * @param qualifier the qualifier * @return the view */ public static View getLastChild(ViewGroup viewGroup, Qualifier qualifier) { for (int i = viewGroup.getChildCount() - 1; i >= 0; i--) { View child = viewGroup.getChildAt(i); if (qualifies(qualifier, child)) { return child; } } return null; } /** * Get children collection. * * @param viewGroup the view group * @return the collection */ public static Collection<View> getChildren(ViewGroup viewGroup) { return getChildren(viewGroup, null); } /** * @param viewGroup * @param qualifier * @return */ public static Collection<View> getChildren(ViewGroup viewGroup, Qualifier qualifier) { return getChildren(viewGroup, qualifier, new ArrayList<>()); } /** * Get children collection. * * @param viewGroup the view group * @param qualifier the qualifier * @param out * @return the collection */ public static Collection<View> getChildren(ViewGroup viewGroup, Qualifier qualifier, Collection<View> out) { for (int i = 0; i < viewGroup.getChildCount(); i++) { View child = viewGroup.getChildAt(i); if (qualifies(qualifier, child)) { out.add(child); } } return out; } /** * Gets ancestors. * * @param view the view * @return the ancestors */ public static Collection<ViewGroup> getAncestors(View view) { return getAncestors(view, null); } /** * Gets ancestors. * * @param view the view * @param qualifier the qualifier * @return the ancestors */ public static Collection<ViewGroup> getAncestors(View view, Qualifier qualifier) { return getAncestors(view, qualifier, new ArrayList<>()); } /** * Gets ancestors. * * @param view the view * @param qualifier the qualifier * @param out * @return the ancestors */ public static Collection<ViewGroup> getAncestors(View view, Qualifier qualifier, Collection<ViewGroup> out) { ViewGroup parent = getContainingViewGroup(view); while (parent != null) { if (qualifies(qualifier, parent)) { out.add(parent); } parent = getContainingViewGroup(parent); } return out; } /** * Get siblings collection. * * @param view the view * @return the collection */ public static Collection<View> getSiblings(View view) { return getSiblings(view, null); } /** * Get siblings collection. * * @param view the view * @param qualifier the qualifier * @return the collection */ public static Collection<View> getSiblings(View view, Qualifier qualifier) { ViewGroup parent = getContainingViewGroup(view); if (parent == null) { return null; } Collection<View> siblings = new ArrayList<>(); for (int i = 0; i < parent.getChildCount(); i++) { View child = parent.getChildAt(i); if (child != view && qualifies(qualifier, child)) { siblings.add(child); } } return siblings; } /** * Get previous sibling view. * * @param view the view * @return the view */ public static View getPreviousSibling(View view) { return getPreviousSibling(view, null); } /** * Get previous sibling view. * * @param view the view * @param qualifier the qualifier * @return the view */ public static View getPreviousSibling(View view, Qualifier qualifier) { ViewGroup parent = getContainingViewGroup(view); if (parent == null) { return null; } for (int i = 0; i < parent.getChildCount(); i++) { View child = parent.getChildAt(i); if (child == view) { for (; i > 0; ) { View sibling = parent.getChildAt(--i); if (qualifies(qualifier, sibling)) { return sibling; } } } } return null; } /** * Get next sibling view. * * @param view the view * @return the view */ public static View getNextSibling(View view) { return getNextSibling(view, null); } /** * Get next sibling view. * * @param view the view * @param qualifier the qualifier * @return the view */ public static View getNextSibling(View view, Qualifier qualifier) { ViewGroup parent = getContainingViewGroup(view); if (parent == null) { return null; } for (int i = 0; i < parent.getChildCount(); i++) { View child = parent.getChildAt(i); if (child == view) { while (i < parent.getChildCount()) { View sibling = parent.getChildAt(++i); if (qualifies(qualifier, sibling)) { return sibling; } } } } return null; } /** * Get previous siblings collection. * * @param view the view * @return the collection */ public static Collection<View> getPreviousSiblings(View view) { return getPreviousSiblings(view, null); } /** * Get previous siblings collection. * * @param view the view * @param qualifier the qualifier * @return the collection */ public static Collection<View> getPreviousSiblings(View view, Qualifier qualifier) { ViewGroup parent = getContainingViewGroup(view); if (parent == null) { return null; } Collection<View> siblings = new ArrayList<>(); for (int i = 0; i < parent.getChildCount(); i++) { View child = parent.getChildAt(i); if (child == view) { break; } if (qualifies(qualifier, child)) { siblings.add(child); } } return siblings; } /** * Get next siblings collection. * * @param view the view * @return the collection */ public static Collection<View> getNextSiblings(View view) { return getNextSiblings(view, null); } /** * Get next siblings collection. * * @param view the view * @param qualifier the qualifier * @return the collection */ public static Collection<View> getNextSiblings(View view, Qualifier qualifier) { ViewGroup parent = getContainingViewGroup(view); if (parent == null) { return null; } Collection<View> siblings = new ArrayList<>(); boolean hasFoundReference = false; for (int i = 0; i < parent.getChildCount(); i++) { View child = parent.getChildAt(i); if (hasFoundReference && qualifies(qualifier, view)) { siblings.add(child); } if (child == view) { hasFoundReference = true; } } return siblings; } /** * Finds the first child in #rootView that is an instance of #clazz * * Use this instead of #findAll with an instanceof Qualifier in order to get typed returns, * e.g., Collection<TextView> textViews = ViewFinder.findAllByClass(someViewGroup, TextView.class); * * @param <T> The type of View subclass to search for. * @param viewGroup The View whose hierarchy should be examined for instances of #clazz. * @param clazz The Class to search for within #rootView. * @return The first child in #rootView this is an instance of #clazz. */ public static <T extends View> T findByClass(ViewGroup viewGroup, Class<T> clazz) { for (int i = 0; i < viewGroup.getChildCount(); i++) { View child = viewGroup.getChildAt(i); if (clazz.isInstance(child)) { return clazz.cast(child); } if (child instanceof ViewGroup) { T match = findByClass((ViewGroup) child, clazz); if (match != null) { return match; } } } return null; } /** * Returns a Collection of View subclasses instances of type T found within #rootView. * * Use this instead of #findAll with an instanceof Qualifier in order to get typed returns, * e.g., Collection<TextView> textViews = ViewFinder.findAllByClass(someViewGroup, TextView.class, null); * * @param <T> The type of View subclass to search for. * @param viewGroup The View whose hierarchy should be examined for instances of #clazz. * @param clazz The Class to search for within #rootView. * @param out A Collection of View subclasses of type T that will be populated with matches found in #rootView. * @return A Collection of View subclasses instances of type T found within #rootView. */ public static <T extends View> Collection<T> findAllByClass(ViewGroup viewGroup, Class<T> clazz, Collection<T> out) { for (int i = 0; i < viewGroup.getChildCount(); i++) { View child = viewGroup.getChildAt(i); if (clazz.isInstance(child)) { out.add(clazz.cast(child)); } if (child instanceof ViewGroup) { findAllByClass((ViewGroup) child, clazz, out); } } return out; } /** * Returns a Collection of View subclasses instances of type T found within #rootView. * * @param <T> The type of View subclass to search for. * @param viewGroup The View whose hierarchy should be examined for instances of #clazz. * @param clazz The Class to search for within #rootView. * @return A Collection of View subclasses instances of type T found within #rootView. */ public static <T extends View> Collection<T> findAllByClass(ViewGroup viewGroup, Class<T> clazz) { return findAllByClass(viewGroup, clazz, new ArrayList<>()); } } |
Add (or amend) your values/attrs.xml to include:
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<resources> <declare-styleable name="SeparatorLinearLayout"> <attr name="separator" format="reference" /> <attr name="separatorHeight" format="integer" /> <attr name="separatorWidth" format="integer" /> </declare-styleable> </resources> |
Some layout:
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<?xml version="1.0" encoding="utf-8"?> <com.qozix.widgets.SeparatorLinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical" app:separator="?android:attr/listDivider"><!-- any drawable or color --> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:padding="12sp" android:text="This is a row" /> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:padding="12sp" android:text="This is a row" /> </com.qozix.widgets.SeparatorLinearLayout> |
And the class:
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package com.qozix.widgets; import android.content.Context; import android.content.res.TypedArray; import android.graphics.Canvas; import android.graphics.Rect; import android.graphics.drawable.Drawable; import android.util.AttributeSet; import android.view.View; import android.widget.LinearLayout; import com.qozix.widgets.R; /** * Created by michaeldunn on 8/15/16. */ public class SeparatorLinearLayout extends LinearLayout { private Drawable mSeparator; private Rect mSeparatorBounds = new Rect(); private int mSeparatorHeight; private int mSeparatorWidth; public SeparatorLinearLayout(Context context) { this(context, null); } public SeparatorLinearLayout(Context context, AttributeSet attrs) { this(context, attrs, 0); } public SeparatorLinearLayout(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); setWillNotDraw(false); TypedArray typedArray = context.getTheme().obtainStyledAttributes(attrs, R.styleable.SeparatorLinearLayout, 0, 0); try { Drawable drawable = typedArray.getDrawable(R.styleable.SeparatorLinearLayout_separator); if (drawable != null) { setSeparator(drawable); } int drawableWidth = typedArray.getInt(R.styleable.SeparatorLinearLayout_separatorWidth, 0); if (drawableWidth != 0) { setSeparatorWidth(drawableWidth); } int drawableHeight = typedArray.getInt(R.styleable.SeparatorLinearLayout_separatorHeight, 0); if (drawableHeight != 0) { setSeparatorHeight(drawableHeight); } } finally { typedArray.recycle(); } } public void setSeparator(Drawable drawable) { mSeparator = drawable; if (mSeparator != null) { mSeparatorHeight = mSeparator.getIntrinsicHeight(); mSeparatorWidth = mSeparator.getIntrinsicWidth(); } } public void setSeparatorHeight(int separatorHeight) { mSeparatorHeight = separatorHeight; } public void setSeparatorWidth(int separatorWidth) { mSeparatorWidth = separatorWidth; } private void drawVerticalSeparators(Canvas canvas) { mSeparatorBounds.left = 0; mSeparatorBounds.right = canvas.getWidth(); for (int i = 0; i < getChildCount() - 1; i++) { View child = getChildAt(i); mSeparatorBounds.top = child.getBottom() - 1; mSeparatorBounds.bottom = mSeparatorBounds.top + mSeparatorHeight; drawDrawableToCanvas(canvas); } } private void drawHorizontalSeparators(Canvas canvas) { mSeparatorBounds.top = 0; mSeparatorBounds.bottom = canvas.getHeight(); for (int i = 0; i < getChildCount() - 1; i++) { View child = getChildAt(i); mSeparatorBounds.left = child.getRight() - 1; mSeparatorBounds.right = mSeparatorBounds.left + mSeparatorWidth; drawDrawableToCanvas(canvas); } } private void drawDrawableToCanvas(Canvas canvas) { mSeparator.setBounds(mSeparatorBounds); mSeparator.draw(canvas); } private void drawSeparators(Canvas canvas) { switch (getOrientation()) { case VERTICAL: drawVerticalSeparators(canvas); break; case HORIZONTAL: drawHorizontalSeparators(canvas); break; } } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); if (mSeparator != null) { drawSeparators(canvas); } } } |
The behavior here isn’t quite what I expected, or gather from the documentation. If you have <activity android:name=”.SomeActivity” android:launchMode=”singleTop” /> Then you start SomeActivity multiple times:
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private void doIt(){ startSomeActivity(); startSomeActivity(); } private void startSomeActivity(){ Intent intent = new Intent(this, SomeActivity.class); startActivity(intent); } |
You’ll get only one instance of SomeActivity at the top of the stack (as the singleTop launch mode promises), but you’ll notice that if you finish() or hit […]
Possibly useful in precomputing layout requirements…
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public static int getDefaultTextSize(Context context) { TypedValue typedValue = new TypedValue(); context.getTheme().resolveAttribute(android.R.attr.textAppearance, typedValue, true); int[] textSizeAttr = new int[] { android.R.attr.textSize }; TypedArray typedArray = context.obtainStyledAttributes(typedValue.data, textSizeAttr); int textSize = typedArray.getDimensionPixelSize(0, -1); typedArray.recycle(); return textSize; } |
When extending a typed class without specifying the type, just pass the type to the subclass’s erasure and specify that type in the reference to the superclass. E.g.,
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public class MyClass<E extends List> {} public class MySubClass<E extends List> extends MyClass<E> {} // E is already declared by the time we get to MyClass, so just reference it - instead of defining it - as a type param for the superclass |
As an example, consider the AOSP class RecyclerView.Adapter, which is declared as:
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public static abstract class Adapter<VH extends ViewHolder> |
A normal concrete implementation is fairly straightforward:
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public class MyAdapter extends Adapter<MyHolder> |
But what if you want […]
Probably unexpected behavior:
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public class Main { public static void main(String[] args) { mew SomeSub(); } public abstract static class SomeSuper { public SomeSuper(){ doInit(); } public abstract void doInit(); } public static class SomeSub extends SomeSuper { public int someIntMember = 3; public void doInit(){ System.out.println(someIntMember); // prints 0, not 3 } } } |
There’s not a direct way to work around this – often initialization or setup methods are used, sometimes with a Factory instance generator.
Butterknife, like most things by Square and/or Jake Wharton, is a very handy, very popular library. One thing that was really nice was how small and simple it was. The latest version, however, is a lot less simple, and requires multiple gradle dependencies and the apt plugin. Not a huge lift, but not exactly as […]
This is a little tricky, and isn’t precisely a version limitation. Here’s why, and how I’ve found the most reliable way to get it. 1. Environment.isExternalStorageRemovable (without parameters) is API 9+, so has broad support. If your devices primary external storage location is removable, then this will return the location you want – done. 2. […]
/EDIT: I’ve created a library (and demo): https://github.com/moagrius/EndlessRecyclerView Most “endless” RecyclerViews wait until the last item is visible, then load more data, which is often fine and probably very more efficient strategy. However, sometimes we need to be a little more responsive, and try not to let the scroll come to a complete stop. Here’s […]
