commit cb8488822cc34c933b8e7f6f0907f4cbb33485d9
author Chet Haase <chet@google.com> Wed Mar 21 14:09:44 2018 -0700
committer Chet Haase <chet@google.com> Wed Apr 11 16:22:47 2018 +0000
tree d25a6aad625040b8829304a1dc2526820ec7fdc4
parent 997e7b7ea43282a9216d205ec291358dfa01136a

Add targetSdk check around new LinearLayout weighted measure behavior

Bug: 73827180
Test: Existing CTS tests in LinearLayoutTest
Change-Id: I88dfde3743d0f954cd275be6a0032fe30ef55c03
(cherry picked from commit 28230e5efa86aa324fef3e95395d61a4518fa804)

core/java/android/os/Build.java

diff --git a/core/java/android/os/Build.java b/core/java/android/os/Build.java
index 8378a82..7162b8a 100644
--- a/core/java/android/os/Build.java
+++ b/core/java/android/os/Build.java
@@ -907,6 +907,8 @@
          * <li>{@link android.app.Service#startForeground Service.startForeground} requires
          * that apps hold the permission
          * {@link android.Manifest.permission#FOREGROUND_SERVICE}.</li>
+         * <li>{@link android.widget.LinearLayout} will always remeasure weighted children,
+         * even if there is no excess space.</li>
          * </ul>
          */
         public static final int P = CUR_DEVELOPMENT; // STOPSHIP Replace with the real version.

core/java/android/widget/LinearLayout.java

diff --git a/core/java/android/widget/LinearLayout.java b/core/java/android/widget/LinearLayout.java
index d32e93c..40f9652 100644
--- a/core/java/android/widget/LinearLayout.java
+++ b/core/java/android/widget/LinearLayout.java
@@ -217,6 +217,17 @@
 
     private int mLayoutDirection = View.LAYOUT_DIRECTION_UNDEFINED;
 
+    /**
+     * Signals that compatibility booleans have been initialized according to
+     * target SDK versions.
+     */
+    private static boolean sCompatibilityDone = false;
+
+    /**
+     * Behavior change in P; always remeasure weighted children, regardless of excess space.
+     */
+    private static boolean sRemeasureWeightedChildren = true;
+
     public LinearLayout(Context context) {
         this(context, null);
     }
@@ -232,6 +243,15 @@
     public LinearLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
         super(context, attrs, defStyleAttr, defStyleRes);
 
+        if (!sCompatibilityDone && context != null) {
+            final int targetSdkVersion = context.getApplicationInfo().targetSdkVersion;
+
+            // Older apps only remeasure non-zero children
+            sRemeasureWeightedChildren = targetSdkVersion >= Build.VERSION_CODES.P;
+
+            sCompatibilityDone = true;
+        }
+
         final TypedArray a = context.obtainStyledAttributes(
                 attrs, com.android.internal.R.styleable.LinearLayout, defStyleAttr, defStyleRes);
 
@@ -917,7 +937,8 @@
         // measurement on any children, we need to measure them now.
         int remainingExcess = heightSize - mTotalLength
                 + (mAllowInconsistentMeasurement ? 0 : consumedExcessSpace);
-        if (skippedMeasure || totalWeight > 0.0f) {
+        if (skippedMeasure
+                || ((sRemeasureWeightedChildren || remainingExcess != 0) && totalWeight > 0.0f)) {
             float remainingWeightSum = mWeightSum > 0.0f ? mWeightSum : totalWeight;
 
             mTotalLength = 0;
@@ -1300,7 +1321,8 @@
         // measurement on any children, we need to measure them now.
         int remainingExcess = widthSize - mTotalLength
                 + (mAllowInconsistentMeasurement ? 0 : usedExcessSpace);
-        if (skippedMeasure || totalWeight > 0.0f) {
+        if (skippedMeasure
+                || ((sRemeasureWeightedChildren || remainingExcess != 0) && totalWeight > 0.0f)) {
             float remainingWeightSum = mWeightSum > 0.0f ? mWeightSum : totalWeight;
 
             maxAscent[0] = maxAscent[1] = maxAscent[2] = maxAscent[3] = -1;