Question

这是图书样本中的代码：

new AlertDialog.Builder(this)
    .setTitle(getResources().getString(R.string.alert_label))
    .setMessage(validationText.toString())
    .setPositiveButton("Continue", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int arg1) {
           // in this case, don't need to do anything other than close alert
        }
    })
.show();

我想了解这段代码，请在几个语句中重写它，以便每个语句只进行一次操作。谢谢！

Answer 1

// Create a builder
AlertDialog.Builder adb = new AlertDialog.Builder(this);

// Set a title
adb.setTitle(getResources().getString(R.string.alert_label));

// Set the dialogs message
adb.setMessage(validationText.toString());

// Set label and even handling of the "positive button"
// 
// NOTE: If you don't want to do anything here except to close the dlg 
// use the next line instead (you don't have to specifiy an event handler)
// adb.setPositiveButton("Continue", null);

adb.setPositiveButton("Continue",
    new android.content.DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int arg1) {
       // in this case, don't need to do anything other than close alert
    }
    });

// Show the dialog
adb.show();

单独的语句，每个语句都在普通的构建器对象上执行。

或者，您可以链接构建器方法以保存一些字符（如您的原始源），但您可以将其编写为更具可读性。为此，请删除每行开头的分号和对象引用。每个构建器方法都返回原始构建器对象，您可以使用该对象在其上运行下一个语句。

这是一个小的，更易读的例子：

new AlertDialog.Builder(this)
.setTitle("Title")
.setMessage("42 is the answer")
.show();

Answer 2

AlertDialog.Builder有许多方法都返回它们运行的AlertDialog.Builder。

这允许你写：

builder.A();
builder.B();
builder.C() ;

as

builder.A().B().C();

我发现这更令人讨厌，但那只是我。

Answer 3

AlerDialog.Builder d = new AlertDialog.Builder(this); // get an Object of AlertDialog.Builder

d.setTitle(getResources().getString(R.string.alert_label)); //Set its title

d.setMessage(validationText.toString()); //set message body

d.setPositiveButton("Continue",new android.content.DialogInterface.OnClickListener() {

    public void onClick(DialogInterface dialog, int arg1) {
       // in this case, don't need to do anything other than close alert
    }
 }); //this dialog will have single button called Continue

d.show(); // this pops up the dialog..

Answer 4

此技术称为Method chaining

Answer 5

尝试在每个之前设置换行符。然后它会更具可读性。

new AlertDialog.Builder(this)
.setTitle(

getResources().getString(R.string.alert_label))

.setMessage(validationText.toString()).setPositiveButton("Continue",

new android.content.DialogInterface.OnClickListener() {
 public void onClick(DialogInterface dialog, int arg1) {
   // in this case, don't need to do anything other than close alert
 }
 })
.show();

AlertDialog - 试图理解这种语法

5 个答案: