1
我已经实现了使用下面的代码扩展ViewGroup的仪表板。但结果并不像我预期的那样显示。仪表板具有按钮作为其子视图，可正确显示，但按钮内的文本具有异常对齐。自定义仪表板按钮文本定位
您是否真的很好解释为什么按钮标签对其容器的大小调整和定位具有定位作用，而一个位置是由XML属性'gravity'设置的？
应该怎么做在按钮中居中文本？
可能需要解释onMeasure（）和onLayout（）方法。据我猜测，第一种方法通过其子视图大小来测量容器（仪表板）大小，第二种方法改变容器内这些子视图的位置并调整它的大小。不是吗？但是，为什么在onMeasure（）中儿童观点的位置和大小会产生影响？
在此先感谢。
MainDashboard.java
public class MainDashboard extends ViewGroup {
/*Attributes: */
private static final float DEFAULT_FACTOR = 0.2f;
private static final float DEFAULT_SPACING = 0.025f;
private static final int DEFAULT_ROW = 1;
private static final int DEFAULT_COL = 1;
private int mMaxChildWidth = 0;
private int mMaxChildHeight = 0;
/*Attribute variables: */
private float mFactor;
private float mSpacing;
private int mRow;
private int mCol;
private DeviceScreenSize dss;
private SCApplication app;
private int ell_size;
public MainDashboard(Context context) {
super(context, null);
}
public MainDashboard(Context context, AttributeSet attrs) {
super(context, attrs, 0);
init(context,attrs);
}
public MainDashboard(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
private void init(Context context, AttributeSet attrs){
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.MainDashboard);
mFactor = a.getFloat(R.styleable.MainDashboard_factor, DEFAULT_FACTOR);
mSpacing = a.getFloat(R.styleable.MainDashboard_spacing, DEFAULT_SPACING);
mRow = a.getInteger(R.styleable.MainDashboard_row, DEFAULT_ROW);
mCol = a.getInteger(R.styleable.MainDashboard_col, DEFAULT_COL);
app = (SCApplication)context.getApplicationContext();
dss= app.getScreenSize();
ell_size = (int) (Math.min(dss.getWidth(),dss.getHeight())*mFactor);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
mMaxChildWidth = 0;
mMaxChildHeight = 0;
// Measure once to find the maximum child size.
int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(
MeasureSpec.getSize(widthMeasureSpec), MeasureSpec.AT_MOST);
int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(
MeasureSpec.getSize(widthMeasureSpec), MeasureSpec.AT_MOST);
final int count = getChildCount();
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() == GONE) {
continue;
}
child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
mMaxChildWidth = Math.max(mMaxChildWidth, child.getMeasuredWidth());
mMaxChildHeight = Math.max(mMaxChildHeight, child.getMeasuredHeight());
}
// Measure again for each child to be exactly the same size.
childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(
mMaxChildWidth, MeasureSpec.EXACTLY);
childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(
mMaxChildHeight, MeasureSpec.EXACTLY);
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() == GONE) {
continue;
}
child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
}
setMeasuredDimension(
resolveSize(mMaxChildWidth, widthMeasureSpec),
resolveSize(mMaxChildHeight, heightMeasureSpec));
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int container_width = r - l;
int container_height = b - t;
final int count = getChildCount();
int visibleCount = 0;
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() == GONE) {
continue;
}
++visibleCount;
}
if (visibleCount == 0) {
return;
}
int left, top;
int hSpace=(int)(mSpacing *container_width),
vSpace=(int)(2 * mSpacing * container_width);
int col, row;
int visibleIndex = 0;
for (int i = 0; i < visibleCount; i++) {
final View child = getChildAt(i);
row = visibleIndex/mCol;
col = visibleIndex % mCol;
left = hSpace * (col + 1) + ell_size * col;
top = vSpace * (row + 1) + ell_size * row;
child.layout(left, top, left + ell_size, top + ell_size);
++visibleIndex;
}
}
}
main.xml中
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:whatever="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/llRoot"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
android:background = "#000000" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="7"
android:gravity="center">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/tvMainTitle"
style="@android:style/TextAppearance.Large"
android:text="@string/main_title"
android:textColor="#4169E1"
/>
</LinearLayout>
<com.sample.myapp.MainDashboard
xmlns:android = "http://schemas.android.com/apk/res/android"
android:id="@+id/dash"
android:layout_width = "match_parent"
android:layout_height = "match_parent"
android:layout_weight = "1"
android:background = "#000000"
whatever:col="4">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn1"
android:text="1"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn2"
android:text="2"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn3"
android:text="3"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn4"
android:text="4"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn5"
android:text="5"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn6"
android:text="6"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn7"
android:text="7"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn8"
android:text="8"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn9"
android:text="9"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn10"
android:text="10"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn11"
android:text="11"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn12"
android:text="12"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn13"
android:text="13"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn14"
android:text="14"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn15"
android:text="15"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/DashboardButton"
android:id="@+id/btn16"
android:text="16"
/>
</com.sample.myapp.MainDashboard>
</LinearLayout>
styles.xml
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<!-- Customize your theme here. -->
<item name="colorPrimary">@color/colorPrimary</item>
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="colorAccent">@color/colorAccent</item>
</style>
<style name = "DashboardButton">
<item name = "android:textSize">14sp</item >
<item name = "android:textStyle">bold</item >
<item name = "android:textColor">#FFFFFF</item>
<item name = "android:gravity">center_horizontal</item >
<item name = "android:layout_gravity">center_vertical</item >
<item name = "android:background">@drawable/defaultbuttonselector</item >
<item name = "android:layout_width">wrap_content</item >
<item name = "android:layout_height">wrap_content</item >
</style>
</resources>
defaultbuttonselector.xml
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item>
<shape
android:shape="rectangle" >
<corners android:radius="10.0dp" />
<stroke
android:width="2dp"
android:color="#4169E1" />
</shape>
</item>
<item android:state_pressed="true">
<shape android:shape="rectangle">
<corners android:radius="10.0dip" />
<stroke
android:width="3dp"
android:color="#00f2ff" />
</shape>
</item>
</selector>
attrs.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="MainDashboard">
<attr name="factor" format="float" />
<attr name="spacing" format="float" />
<attr name="row" format="integer" />
<attr name="col" format="integer" />
</declare-styleable>
</resources>
MainActivity.java
public class MainActivity extends AppCompatActivity{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
