定义模式：
将构建过程和表示过程进行分离，让参数构建过程变得更加的简单和直观。
builder模式的实例：
- okhttp
OkHttpClient okHttpClient= new OkHttpClient.Builder()
.readTimeout(10, TimeUnit.SECONDS)
.connectTimeout(10,TimeUnit.SECONDS)
.build();
源码：
public class OkHttpClient implements Cloneable, Call.Factory, WebSocket.Factory {
public OkHttpClient() {
this(new Builder());
}
//Builder.builder()方法调用这个构造函数并把builder传进来
OkHttpClient(Builder builder) {
this.dispatcher = builder.dispatcher;
this.proxy = builder.proxy;
...
}
public static final class Builder {
public Builder() {
dispatcher = new Dispatcher();
protocols = DEFAULT_PROTOCOLS;
connectionSpecs = DEFAULT_CONNECTION_SPECS;
proxySelector = ProxySelector.getDefault();
cookieJar = CookieJar.NO_COOKIES;
socketFactory = SocketFactory.getDefault();
hostnameVerifier = OkHostnameVerifier.INSTANCE;
certificatePinner = CertificatePinner.DEFAULT;
proxyAuthenticator = Authenticator.NONE;
authenticator = Authenticator.NONE;
connectionPool = new ConnectionPool();
dns = Dns.SYSTEM;
followSslRedirects = true;
followRedirects = true;
retryOnConnectionFailure = true;
connectTimeout = 10_000;
readTimeout = 10_000;
writeTimeout = 10_000;
}
public OkHttpClient build() {
return new OkHttpClient(this);
}
}
}
- Dialog
//显示基本的AlertDialog
private void showDialog(Context context) {
AlertDialog.Builder builder = new AlertDialog.Builder(context);
builder.setIcon(R.drawable.icon);
builder.setTitle("头部");
builder.setMessage("内容");
builder.setPositiveButton("Button1",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
setTitle("点击了对话框上的Button1");
}
})
.setNeutralButton("Button2",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
setTitle("点击了对话框上的Button2");
}
});
builder.create().show(); // 构建AlertDialog， 并且显示
}
// AlertDialog
public class AlertDialog extends Dialog implements DialogInterface {
// Controller, 接受Builder成员变量P中的各个参数
private AlertController mAlert;
// 构造函数
protected AlertDialog(Context context, int theme) {
this(context, theme, true);
}
// 4 : 构造AlertDialog
AlertDialog(Context context, int theme, boolean createContextWrapper) {
super(context, resolveDialogTheme(context, theme), createContextWrapper);
mWindow.alwaysReadCloseOnTouchAttr();
mAlert = new AlertController(getContext(), this, getWindow());
}
// 实际上调用的是mAlert的setTitle方法
@Override
public void setTitle(CharSequence title) {
super.setTitle(title);
mAlert.setTitle(title);
}
// 实际上调用的是mAlert的setCustomTitle方法
public void setCustomTitle(View customTitleView) {
mAlert.setCustomTitle(customTitleView);
}
public void setMessage(CharSequence message) {
mAlert.setMessage(message);
}
// AlertDialog其他的代码省略
// ************ Builder为AlertDialog的内部类 *******************
public static class Builder {
// 1 : 存储AlertDialog的各个参数, 例如title, message, icon等.
private final AlertController.AlertParams P;
// 属性省略
/**
* Constructor using a context for this builder and the {@link AlertDialog} it creates.
*/
public Builder(Context context) {
this(context, resolveDialogTheme(context, 0));
}
public Builder(Context context, int theme) {
P = new AlertController.AlertParams(new ContextThemeWrapper(
context, resolveDialogTheme(context, theme)));
mTheme = theme;
}
// Builder的其他代码省略 ......
// 2 : 设置各种参数
public Builder setTitle(CharSequence title) {
P.mTitle = title;
return this;
}
public Builder setMessage(CharSequence message) {
P.mMessage = message;
return this;
}
public Builder setIcon(int iconId) {
P.mIconId = iconId;
return this;
}
public Builder setPositiveButton(CharSequence text, final OnClickListener listener) {
P.mPositiveButtonText = text;
P.mPositiveButtonListener = listener;
return this;
}
public Builder setView(View view) {
P.mView = view;
P.mViewSpacingSpecified = false;
return this;
}
// 3 : 构建AlertDialog, 传递参数
public AlertDialog create() {
// 调用new AlertDialog构造对象， 并且将参数传递个体AlertDialog
final AlertDialog dialog = new AlertDialog(P.mContext, mTheme, false);
// 5 : 将P中的参数应用的dialog中的mAlert对象中
P.apply(dialog.mAlert);
dialog.setCancelable(P.mCancelable);
if (P.mCancelable) {
dialog.setCanceledOnTouchOutside(true);
}
dialog.setOnCancelListener(P.mOnCancelListener);
if (P.mOnKeyListener != null) {
dialog.setOnKeyListener(P.mOnKeyListener);
}
return dialog;
}
}
}
public void apply(AlertController dialog) {
if (mCustomTitleView != null) {
dialog.setCustomTitle(mCustomTitleView);
} else {
if (mTitle != null) {
dialog.setTitle(mTitle);
}
if (mIcon != null) {
dialog.setIcon(mIcon);
}
if (mIconId >= 0) {
dialog.setIcon(mIconId);
}
if (mIconAttrId > 0) {
dialog.setIcon(dialog.getIconAttributeResId(mIconAttrId));
}
}
if (mMessage != null) {
dialog.setMessage(mMessage);
}
if (mPositiveButtonText != null) {
dialog.setButton(DialogInterface.BUTTON_POSITIVE, mPositiveButtonText,
mPositiveButtonListener, null);
}
if (mNegativeButtonText != null) {
dialog.setButton(DialogInterface.BUTTON_NEGATIVE, mNegativeButtonText,
mNegativeButtonListener, null);
}
if (mNeutralButtonText != null) {
dialog.setButton(DialogInterface.BUTTON_NEUTRAL, mNeutralButtonText,
mNeutralButtonListener, null);
}
if (mForceInverseBackground) {
dialog.setInverseBackgroundForced(true);
}
// For a list, the client can either supply an array of items or an
// adapter or a cursor
if ((mItems != null) || (mCursor != null) || (mAdapter != null)) {
createListView(dialog);
}
if (mView != null) {
if (mViewSpacingSpecified) {
dialog.setView(mView, mViewSpacingLeft, mViewSpacingTop, mViewSpacingRight,
mViewSpacingBottom);
} else {
dialog.setView(mView);
}
}
}
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