Add max line attribute to specify the maximum number of flex lines. (#424)

Add maxLine support from the XML

Author: thagikura

flexbox/src/androidTest/java/com/google/android/flexbox/FakeFlexContainer.kt

@@ -18,6 +18,7 @@ package com.google.android.flexbox
 
 import android.view.View
 import android.view.ViewGroup
+import com.google.android.flexbox.FlexContainer.NOT_SET
 
 /**
  * Fake implementation of [FlexContainer].
@@ -43,6 +44,8 @@ internal class FakeFlexContainer : FlexContainer {
     @AlignContent
     private var alignContent = AlignContent.STRETCH
 
+    private var maxLine = -1
+
     override fun getFlexItemCount() = views.size
 
     override fun getFlexItemAt(index: Int) = views[index]
@@ -95,6 +98,12 @@ internal class FakeFlexContainer : FlexContainer {
         this.alignItems = alignItems
     }
 
+    override fun getMaxLine(): Int = this.maxLine
+
+    override fun setMaxLine(maxLine: Int) {
+        this.maxLine = maxLine
+    }
+
     override fun getFlexLines() = flexLines
 
     override fun isMainAxisDirectionHorizontal(): Boolean {

flexbox/src/androidTest/java/com/google/android/flexbox/test/FlexboxAndroidTest.kt

@@ -3967,6 +3967,28 @@ class FlexboxAndroidTest {
         assertThat(view2.right, `is`(240))
     }
 
+    @Test
+    @FlakyTest
+    @Throws(Throwable::class)
+    fun testMaxLines() {
+        val activity = activityRule.activity
+        val flexboxLayout = createFlexboxLayout(R.layout.activity_empty_children,
+                object : Configuration {
+                    override fun apply(flexboxLayout: FlexboxLayout) {
+                        flexboxLayout.maxLine = 3
+                        for (i in 1..50) {
+                            val textView = createTextView(activity, i.toString(), 0)
+                            val lp = FlexboxLayout.LayoutParams(100, 100)
+                            lp.flexShrink = 0f
+                            textView.layoutParams = lp
+                            flexboxLayout.addView(textView)
+                        }
+                    }
+                })
+        assertThat(flexboxLayout.childCount, `is`(50))
+        assertThat(flexboxLayout.flexLines.size, `is`(3))
+    }
+
     @Throws(Throwable::class)
     private fun createFlexboxLayout(@LayoutRes activityLayoutResId: Int,
                                     configuration: Configuration = Configuration.EMPTY): FlexboxLayout {

flexbox/src/androidTest/java/com/google/android/flexbox/test/FlexboxLayoutManagerTest.kt

@@ -3310,6 +3310,30 @@ class FlexboxLayoutManagerTest {
         assertThat(layoutManager.getChildAt(0).top, `is`(0))
     }
 
+    @Test
+    @FlakyTest
+    @Throws(Throwable::class)
+    fun testMaxLine() {
+        val activity = activityRule.activity
+        val layoutManager = FlexboxLayoutManager(activity)
+        val adapter = TestAdapter()
+        activityRule.runOnUiThread {
+            activity.setContentView(R.layout.recyclerview)
+            val recyclerView = activity.findViewById<RecyclerView>(R.id.recyclerview)
+            layoutManager.flexDirection = FlexDirection.ROW
+            layoutManager.maxLine = 3
+            recyclerView.layoutManager = layoutManager
+            recyclerView.adapter = adapter
+            for (i in 1..50) {
+                val lp = createLayoutParams(activity, 100, 70)
+                lp.flexShrink = 0f
+                adapter.addItem(lp)
+            }
+        }
+        InstrumentationRegistry.getInstrumentation().waitForIdleSync()
+        assertThat(layoutManager.flexLines.size, `is`(3))
+    }
+
     /**
      * Creates a new flex item.
      *

flexbox/src/main/java/com/google/android/flexbox/FlexContainer.java

@@ -26,6 +26,8 @@
  */
 interface FlexContainer {
 
+    int NOT_SET = -1;
+
     /**
      * @return the number of flex items contained in the flex container.
      */
@@ -270,6 +272,18 @@ interface FlexContainer {
      */
     void setFlexLines(List<FlexLine> flexLines);
 
+    /**
+     * @return the current value of the maximum number of flex lines. If not set, {@link #NOT_SET}
+     * is returned.
+     */
+    int getMaxLine();
+
+    /**
+     *
+     * @param maxLine the int value, which specifies the maximum number of flex lines
+     */
+    void setMaxLine(int maxLine);
+
     /**
      * @return the list of the flex lines including dummy flex lines (flex line that doesn't have
      * any flex items in it but used for the alignment along the cross axis), which aren't included

flexbox/src/main/java/com/google/android/flexbox/FlexboxHelper.java

@@ -18,6 +18,7 @@
 
 import static android.support.v7.widget.RecyclerView.NO_POSITION;
 
+import static com.google.android.flexbox.FlexContainer.NOT_SET;
 import static com.google.android.flexbox.FlexItem.FLEX_BASIS_PERCENT_DEFAULT;
 
 import android.support.annotation.NonNull;
@@ -498,7 +499,7 @@ void calculateFlexLines(FlexLinesResult result, int mainMeasureSpec,
                     getViewMeasuredSizeMain(child, isMainHorizontal)
                             + getFlexItemMarginStartMain(flexItem, isMainHorizontal) +
                             getFlexItemMarginEndMain(flexItem, isMainHorizontal),
-                    flexItem, i, indexInFlexLine)) {
+                    flexItem, i, indexInFlexLine, flexLines.size())) {
                 if (flexLine.getItemCountNotGone() > 0) {
                     addFlexLine(flexLines, flexLine, i > 0 ? i - 1 : 0, sumCrossSize);
                     sumCrossSize += flexLine.mCrossSize;
@@ -823,12 +824,15 @@ private int getFlexItemMarginEndCross(FlexItem flexItem, boolean isMainHorizonta
      * @param childLength   the length of a child view which is to be collected to the flex line
      * @param flexItem      the LayoutParams for the view being determined whether a new flex line
      *                      is needed
+     * @param index         the index of the view being added within the entire flex container
+     * @param indexInFlexLine the index of the view being added within the current flex line
+     * @param flexLinesSize the number of the existing flexlines size
      * @return {@code true} if a wrap is required, {@code false} otherwise
      * @see FlexContainer#getFlexWrap()
      * @see FlexContainer#setFlexWrap(int)
      */
     private boolean isWrapRequired(View view, int mode, int maxSize, int currentLength,
-            int childLength, FlexItem flexItem, int index, int indexInFlexLine) {
+            int childLength, FlexItem flexItem, int index, int indexInFlexLine, int flexLinesSize) {
         if (mFlexContainer.getFlexWrap() == FlexWrap.NOWRAP) {
             return false;
         }
@@ -838,6 +842,12 @@ private boolean isWrapRequired(View view, int mode, int maxSize, int currentLeng
         if (mode == View.MeasureSpec.UNSPECIFIED) {
             return false;
         }
+        int maxLine = mFlexContainer.getMaxLine();
+        // Judge the condition by adding 1 to the current flexLinesSize because the flex line
+        // being computed isn't added to the flexLinesSize.
+        if (maxLine != NOT_SET && maxLine <= flexLinesSize + 1) {
+            return false;
+        }
         int decorationLength =
                 mFlexContainer.getDecorationLengthMainAxis(view, index, indexInFlexLine);
         if (decorationLength > 0) {

flexbox/src/main/java/com/google/android/flexbox/FlexboxLayout.java

@@ -56,6 +56,7 @@
  * <li>{@code dividerDrawable}</li>
  * <li>{@code dividerDrawableHorizontal}</li>
  * <li>{@code dividerDrawableVertical}</li>
+ * <li>{@code maxLine}</li>
  * </ul>
  * for the FlexboxLayout.
  *
@@ -114,6 +115,11 @@ public class FlexboxLayout extends ViewGroup implements FlexContainer {
      */
     private int mAlignContent;
 
+    /**
+     * The current value of the {@link }
+     */
+    private int mMaxLine = NOT_SET;
+
     /**
      * The int definition to be used as the arguments for the {@link #setShowDivider(int)},
      * {@link #setShowDividerHorizontal(int)} or {@link #setShowDividerVertical(int)}.
@@ -218,6 +224,7 @@ public FlexboxLayout(Context context, AttributeSet attrs, int defStyleAttr) {
                 .getInt(R.styleable.FlexboxLayout_justifyContent, JustifyContent.FLEX_START);
         mAlignItems = a.getInt(R.styleable.FlexboxLayout_alignItems, AlignItems.STRETCH);
         mAlignContent = a.getInt(R.styleable.FlexboxLayout_alignContent, AlignContent.STRETCH);
+        mMaxLine = a.getInt(R.styleable.FlexboxLayout_maxLine, NOT_SET);
         Drawable drawable = a.getDrawable(R.styleable.FlexboxLayout_dividerDrawable);
         if (drawable != null) {
             setDividerDrawableHorizontal(drawable);
@@ -1205,6 +1212,19 @@ public void setAlignContent(@AlignContent int alignContent) {
         }
     }
 
+    @Override
+    public int getMaxLine() {
+        return mMaxLine;
+    }
+
+    @Override
+    public void setMaxLine(int maxLine) {
+        if (mMaxLine != maxLine) {
+            mMaxLine = maxLine;
+            requestLayout();
+        }
+    }
+
     /**
      * @return the flex lines composing this flex container. This method returns a copy of the
      * original list excluding a dummy flex line (flex line that doesn't have any flex items in it

flexbox/src/main/java/com/google/android/flexbox/FlexboxLayoutManager.java

@@ -88,6 +88,8 @@ public class FlexboxLayoutManager extends RecyclerView.LayoutManager implements
      */
     private int mAlignItems;
 
+    private int mMaxLine = NOT_SET;
+
     /**
      * True if the layout direction is right to left, false otherwise.
      */
@@ -353,6 +355,19 @@ public void setAlignContent(@AlignContent int alignContent) {
                 + "if you need to use this attribute.");
     }
 
+    @Override
+    public int getMaxLine() {
+        return mMaxLine;
+    }
+
+    @Override
+    public void setMaxLine(int maxLine) {
+        if (mMaxLine != maxLine) {
+            mMaxLine = maxLine;
+            requestLayout();
+        }
+    }
+
     @Override
     public List<FlexLine> getFlexLines() {
         List<FlexLine> result = new ArrayList<>(mFlexLines.size());

flexbox/src/main/res/values/attrs.xml

@@ -82,6 +82,13 @@ limitations under the License.
             <flag name="middle" value="2" />
             <flag name="end" value="4" />
         </attr>
+
+        <!--
+            The attribute that specifies the maximum number of flex lines. This attribute is
+            effective only when the flexWrap attribute is "wrap" or "wrap_reverse".
+        -->
+        <attr name="maxLine" format="integer" />
+
     </declare-styleable>
 
     <declare-styleable name="FlexboxLayout_Layout">