LayoutParams詳解
非常好的參考：
https://www.jianshu.com/p/36b200a0bff4
動態佈局：
如果想要代碼動態寫出上面的佈局，就需要使用 LayoutParams 這個關鍵類了
LayoutParams 的作用是：子控件告訴父控件，自己要如何佈局。
在添加到父佈局時，設置 LayoutParams，通知父佈局如何擺放自己
<span style="color:#cccccc"><code class="language-java">ll.<span style="color:#f08d49">addView</span>(vt, layoutParams);<span style="color:#999999">// 在添加到父佈局的時候</span></code></span>
利用setLayoutParams方法對控件的layout進行佈局更新
<span style="color:#000000"><span style="color:#cccccc"><code class="language-css">textView.<span style="color:#f08d49">setLayoutParams</span>(textParams);</code></span></span>
<span style="color:#000000"><span style="color:#cccccc"><code class="language-csharp"> <span style="color:#f8c555">RelativeLayout<span style="color:#cccccc">.</span>LayoutParams</span> <span style="color:#cc99cd">params</span> <span style="color:#67cdcc">=</span> <span style="color:#cc99cd">new</span> <span style="color:#f8c555">RelativeLayout<span style="color:#cccccc">.</span>LayoutParams</span>(mVgLp);
<span style="color:#cc99cd">params</span>.<span style="color:#f08d49">addRule</span>(RelativeLayout.ALIGN_PARENT_BOTTOM);
<span style="color:#cc99cd">params</span>.<span style="color:#f08d49">addRule</span>(RelativeLayout.ALIGN_PARENT_RIGHT);
mIv.<span style="color:#f08d49">setLayoutParams</span>(<span style="color:#cc99cd">params</span>);</code></span></span>
我們發現，在對 LinearLayout 和 TextView 的 都不設置 LayoutParams 的情況下，
LinearLayout 使用
MATCH_PARENT，而 TextView 使用 WRAP_CONTENT，至於爲什麼，我們要分析一下源碼。
ViewGroup裏面的addview（）；
所以測量由父類控制餓了
public void addView(View child, int index) {
if (child == null) {
throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup");
}
LayoutParams params = child.getLayoutParams();
if (params == null) {
params = generateDefaultLayoutParams();
if (params == null) {
throw new IllegalArgumentException("generateDefaultLayoutParams() cannot return null");
}
}
addView(child, index, params);
}
動態設置view的padding
private void changesize(){
if(weeklyRewardObtainTv.getText()!=null&&weeklyRewardObtainTv.getText().toString()!=null&&weeklyRewardObtainTv.getText().toString().length()>=10){
int left=weeklyRewardObtainTv.getPaddingLeft();
int top=weeklyRewardObtainTv.getPaddingTop();
int bottom=weeklyRewardObtainTv.getPaddingBottom();
int right=weeklyRewardObtainTv.getPaddingRight();
weeklyRewardObtainTv.setPadding(DensityUtil.dip2px(ActivityWeeklyReward.this,53),top,right,bottom);
}
}
雖然setContentView()方法大家都會用，但實際上Android界面顯示的原理要比我們所看到的東西複雜得多。任何一個Activity中顯示的界面其實主要都由兩部分組成，標題欄和內容佈局。標題欄就是在很多界面頂部顯示的那部分內容，比如剛剛我們的那個例子當中就有標題欄，可以在代碼中控制讓它是否顯示。而內容佈局就是一個FrameLayout，這個佈局的id叫作content，我們調用setContentView()方法時所傳入的佈局其實就是放到這個FrameLayout中的，這也是爲什麼這個方法名叫作setContentView()，而不是叫setView()。
最後再附上一張Activity窗口的組成圖吧，以便於大家更加直觀地理解：
LayoutInflater的基本用法有2種：
1：LayoutInflater layoutInflater = LayoutInflater.from(context);
2 ：LayoutInflater layoutInflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
第一種方法是第二種的封裝簡寫。
得到了LayoutInflater的實例之後就可以調用它的inflate()方法來加載佈局了，：layoutInflater.inflate(resourceId, root);
那LayoutInflater 是如何工作的呢 ？
LayoutInflater其實就是使用Android提供的pull解析方式來解析佈局文件的。
LayoutInflater實戰用法舉例：
把一個自定義動態添加到一個佈局裏面
1.自定義了一個view
public class LayoutRunHealthCheck extends FrameLayout implements View.OnClickListener {
private LinearLayout textViewClose;
private HealthAnimationCircleProgressBar healthAnimationCircleProgressBar;
private TextView tv_body_socre, tv_body_des, tv_body_detail, tv_start;
private TextView tv_face_score;
private SimpleDraweeView simpleDraweeView;
private RelativeLayout layoutStart;
private void buildView() {
View view = LayoutInflater.from(context).inflate(R.layout.layout_run_health, null);
textViewClose = view.findViewById(R.id.tv_close);
tv_body_socre = view.findViewById(R.id.tv_body_socre);
tv_body_des = view.findViewById(R.id.tv_body_des);
tv_body_detail = view.findViewById(R.id.tv_body_detail);
tv_start = view.findViewById(R.id.tv_start);
layoutStart = view.findViewById(R.id.layout_start);
simpleDraweeView = view.findViewById(R.id.body_feature);
tv_face_score = view.findViewById(R.id.tv_face_score);
healthAnimationCircleProgressBar = view.findViewById(R.id.cpb_face_score);
textViewClose.setOnClickListener(this);
layoutStart.setOnClickListener(this);
view.setPadding(0, 0, 0, DensityUtil.dip2px(context, 0));
this.addView(view);
iniView();
setData();
}
2.佈局裏面設置
<LinearLayout
android:id="@+id/frame_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"></LinearLayout>
3.在代碼裏面動態添加：
frameLayout = bottomView.findViewById(R.id.frame_layout);
addHealthView();
if (layoutRunHealthCheck == null && activity != null) {
layoutRunHealthCheck = new LayoutRunHealthCheck(activity, type, healthListener);
frameLayout.addView(layoutRunHealthCheck);
LayoutInflater源碼分析：
public View inflate(XmlPullParser parser, @Nullable ViewGroup root, boolean attachToRoot) {
synchronized (mConstructorArgs) {
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "inflate");
final Context inflaterContext = mContext;
final AttributeSet attrs = Xml.asAttributeSet(parser);
Context lastContext = (Context) mConstructorArgs[0];
mConstructorArgs[0] = inflaterContext;
View result = root;
try {
// Look for the root node.
int type;
while ((type = parser.next()) != XmlPullParser.START_TAG &&
type != XmlPullParser.END_DOCUMENT) {
// Empty
}
if (type != XmlPullParser.START_TAG) {
throw new InflateException(parser.getPositionDescription()
+ ": No start tag found!");
}
final String name = parser.getName();
if (DEBUG) {
System.out.println("**************************");
System.out.println("Creating root view: "
+ name);
System.out.println("**************************");
}
if (TAG_MERGE.equals(name)) {
if (root == null || !attachToRoot) {
throw new InflateException("<merge /> can be used only with a valid "
+ "ViewGroup root and attachToRoot=true");
}
rInflate(parser, root, inflaterContext, attrs, false);
} else {
// Temp is the root view that was found in the xml
final View temp = createViewFromTag(root, name, inflaterContext, attrs);
ViewGroup.LayoutParams params = null;
if (root != null) {
if (DEBUG) {
System.out.println("Creating params from root: " +
root);
}
// Create layout params that match root, if supplied
params = root.generateLayoutParams(attrs);
if (!attachToRoot) {
// Set the layout params for temp if we are not
// attaching. (If we are, we use addView, below)
temp.setLayoutParams(params);
}
}
if (DEBUG) {
System.out.println("-----> start inflating children");
}
// Inflate all children under temp against its context.
rInflateChildren(parser, temp, attrs, true);
if (DEBUG) {
System.out.println("-----> done inflating children");
}
// We are supposed to attach all the views we found (int temp)
// to root. Do that now.
if (root != null && attachToRoot) {
root.addView(temp, params);
}
// Decide whether to return the root that was passed in or the
// top view found in xml.
if (root == null || !attachToRoot) {
result = temp;
}
}
} catch (XmlPullParserException e) {
final InflateException ie = new InflateException(e.getMessage(), e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} catch (Exception e) {
final InflateException ie = new InflateException(parser.getPositionDescription()
+ ": " + e.getMessage(), e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} finally {
// Don't retain static reference on context.
mConstructorArgs[0] = lastContext;
mConstructorArgs[1] = null;
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
return result;
}
}
發現merge，include標籤，tag標籤也在這個類裏面
public abstract class LayoutInflater {
private static final String TAG = LayoutInflater.class.getSimpleName();
private static final boolean DEBUG = false;
/** Empty stack trace used to avoid log spam in re-throw exceptions. */
private static final StackTraceElement[] EMPTY_STACK_TRACE = new StackTraceElement[0];
/**
* This field should be made private, so it is hidden from the SDK.
* {@hide}
*/
protected final Context mContext;
// these are optional, set by the caller
private boolean mFactorySet;
private Factory mFactory;
private Factory2 mFactory2;
private Factory2 mPrivateFactory;
private Filter mFilter;
final Object[] mConstructorArgs = new Object[2];
static final Class<?>[] mConstructorSignature = new Class[] {
Context.class, AttributeSet.class};
private static final HashMap<String, Constructor<? extends View>> sConstructorMap =
new HashMap<String, Constructor<? extends View>>();
private HashMap<String, Boolean> mFilterMap;
private TypedValue mTempValue;
private static final String TAG_MERGE = "merge";
private static final String TAG_INCLUDE = "include";
private static final String TAG_1995 = "blink";
private static final String TAG_REQUEST_FOCUS = "requestFocus";
private static final String TAG_TAG = "tag";
2. 如果root不爲null，attachToRoot設爲true，則會給加載的佈局文件的指定一個父佈局，即root。
3. 如果root不爲null，attachToRoot設爲false，則會將佈局文件最外層的所有layout屬性進行設置，當該view被添加到父view當中時，這些layout屬性會自動生效。
4. 在不設置attachToRoot參數的情況下，如果root不爲null，attachToRoot參數默認爲true。
private View createViewFromTag(View parent, String name, Context context, AttributeSet attrs) {
return createViewFromTag(parent, name, context, attrs, false);
}
問題：控件的大小怎麼調試都沒有用，外面少了一層父佈局。首先View必須存在於一個佈局中？？？、
1.progrossbar的高度問題
2.linearylayout的高度問題
3.場景分析：通過一個viewPager自定義banner？ 發現 viewPager wrap的高度不生效
原理是：viewPager重寫了onMesure。固定了自己的高度。然後測量了子view
viewpager本來是用來切換整個屏幕的。不是用來做banner的。
所以高度要自己測量高度。
測量原理：樹的深度變量。
解決辦法：重寫onMesure方法
先度量子view然後再度量自己。
這樣是不正確的，要用到LayoutParams才行
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int height = 0;
for(int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
int h = child.getMeasuredHeight();
if(h > height) height = h;
}
heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
一個viewGroup。父類給他一個參考值，同時要先度量子view。才能確定
有點像view的時間分發。
通過源碼發現：測量自己之前先測量自己都子view
ViewPager源碼：
setMeasuredDimension：測量自己
LayoutParams：子空間的參數測量
MeasureSpec.makeMeasureSpec(widthSize, widthMode); 測量的計算模式
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// For simple implementation, our internal size is always 0.
// We depend on the container to specify the layout size of
// our view. We can't really know what it is since we will be
// adding and removing different arbitrary views and do not
// want the layout to change as this happens.
setMeasuredDimension(getDefaultSize(0, widthMeasureSpec),
getDefaultSize(0, heightMeasureSpec));
final int measuredWidth = getMeasuredWidth();
final int maxGutterSize = measuredWidth / 10;
mGutterSize = Math.min(maxGutterSize, mDefaultGutterSize);
// Children are just made to fill our space.
int childWidthSize = measuredWidth - getPaddingLeft() - getPaddingRight();
int childHeightSize = getMeasuredHeight() - getPaddingTop() - getPaddingBottom();
/*
* Make sure all children have been properly measured. Decor views first.
* Right now we cheat and make this less complicated by assuming decor
* views won't intersect. We will pin to edges based on gravity.
*/
int size = getChildCount();
for (int i = 0; i < size; ++i) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
if (lp != null && lp.isDecor) {
final int hgrav = lp.gravity & Gravity.HORIZONTAL_GRAVITY_MASK;
final int vgrav = lp.gravity & Gravity.VERTICAL_GRAVITY_MASK;
int widthMode = MeasureSpec.AT_MOST;
int heightMode = MeasureSpec.AT_MOST;
boolean consumeVertical = vgrav == Gravity.TOP || vgrav == Gravity.BOTTOM;
boolean consumeHorizontal = hgrav == Gravity.LEFT || hgrav == Gravity.RIGHT;
if (consumeVertical) {
widthMode = MeasureSpec.EXACTLY;
} else if (consumeHorizontal) {
heightMode = MeasureSpec.EXACTLY;
}
int widthSize = childWidthSize;
int heightSize = childHeightSize;
if (lp.width != LayoutParams.WRAP_CONTENT) {
widthMode = MeasureSpec.EXACTLY;
if (lp.width != LayoutParams.MATCH_PARENT) {
widthSize = lp.width;
}
}
if (lp.height != LayoutParams.WRAP_CONTENT) {
heightMode = MeasureSpec.EXACTLY;
if (lp.height != LayoutParams.MATCH_PARENT) {
heightSize = lp.height;
}
}
final int widthSpec = MeasureSpec.makeMeasureSpec(widthSize, widthMode);
final int heightSpec = MeasureSpec.makeMeasureSpec(heightSize, heightMode);
child.measure(widthSpec, heightSpec);
MeasureSpec.makeMeasureSpec(widthSize, widthMode);
makeMeasuerMespect：度量計算：把參數轉成具體指
LayoutParams 也經常用到。
：度量計算：把參數轉成具體指
LayoutParams ====== ====轉爲100dp
fragment 裏面的getactivity==null的原因。
比如：推送的時候，點擊通知欄。因爲他們不在同一個進程
LayoutInflate使用：setcontentview。
第二個：adapter裏面使用
LayoutInflate的調用原理：
裏面如何解析including和其他3種方式
LayoutInflate相關的地方
有的時候高度無效，和根佈局有關係。多添加一層view，設置寬高就可以額。
onmesure什麼時候觸發：
1.父類調用一次
2.onlayout的時候又去調用次
4.類似的情況，recyleView裏面的item高度問題。同樣可以
看源碼工具：source insight
參考博客：
360懸浮球實現