當控制項本身layout_width設定為fill_parent的時候，layout_weight數值越小，所佔空間越大，但儘可能大是有限度的，即fill_parent.
當控制項本身layout_width設定為wrap_content的時候，layout_weight數值越小，所佔空間也越小，但這個小是有限度的，即wrap_content.
例子
看了一下源碼,雖說不太懂,但瞭解了下大概意思,按照自己的理解總結一下,直接寫一下簡化的代碼吧(下面的代碼是LinearLayout源檔案中一部分的精簡,變數名稱含義可能不準確,為敘述方便暫作此解釋):
| 代碼如下 |
複製代碼 |
//Either expand children with weight to take up available space or
// shrink them if they extend beyond our current bounds
int delta = widthSize - mTotalLength;
if (delta != 0 && totalWeight > 0.0f) {
float weightSum = mWeightSum > 0.0f ? mWeightSum : totalWeight;
for (int i = 0; i < count; ++i) {
final View child = getVirtualChildAt(i); if (child == null || child.getVisibility() == View.GONE) {
continue;
}
final LinearLayout.LayoutParams lp =
(LinearLayout.LayoutParams) child.getLayoutParams(); float childExtra = lp.weight;
if (childExtra > 0) {
int share = (int) (childExtra * delta / weightSum);
weightSum -= childExtra;
delta -= share;
int childWidth = child.getMeasuredWidth() + share;
if (childWidth < 0) {
childWidth = 0;
}
}
}
} |
變數含義
widthSize: LinearLayout的寬度
mTotalLength: 所有子View的寬度的和(還沒用考慮layout_weight)
totalWeight: 所有子View的layout_weight的和
mWeihtSUm: LinearLayout的android:weightSum屬性
過程分析:
首先計算出額外空間(可以為負)如果額外空間不為0並且有子View的layout_weight不為0的話按layout_weight分配額外空間:
| 代碼如下 |
複製代碼 |
int delta = widthSize - mTotalLength;
if (delta != 0 && totalWeight > 0.0f) {
...
} |
如果LinearLayout設定了weightSum則覆蓋子View的layout_weight的和:
| 代碼如下 |
複製代碼 |
float weightSum = mWeightSum > 0.0f ? mWeightSum : totalWeight; |
然後遍曆LinearLayout的子項目,如果不為null且Visibility不為GONE的話,取得它的LayoutParams,如果它的layout_weight大於0,根據weightSum與它的weight計算出分配給它的額外空間
| 代碼如下 |
複製代碼 |
if (childExtra > 0) {
int share = (int) (childExtra * delta / weightSum);
weightSum -= childExtra;
delta -= share; int childWidth = child.getMeasuredWidth() + share;
if (childWidth < 0) {
childWidth = 0;
}
} |
例子
| 代碼如下 |
複製代碼 |
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<LinearLayout
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1">
<TextView
android:text="redwwwwwww"
android:gravity="center_horizontal"
android:background="#aa0000"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="1"/>
<TextView
android:text="green"
android:gravity="center_horizontal"
android:background="#00aa00"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="2"/>
<TextView
android:text="blue"
android:gravity="center_horizontal"
android:background="#0000aa"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="3"/>
<TextView
android:text="yellow"
android:gravity="center_horizontal"
android:background="#aaaa00"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="4"/>
</LinearLayout>
</LinearLayout>
|
