在Android中LayoutInflater的用途是什么?
当前回答
当你在ListView中使用自定义视图时，你必须定义行布局。 你创建了一个xml，你放置android小部件，然后在适配器的代码中，你必须这样做:
public MyAdapter(Context context, List<MyObject> objects) extends ArrayAdapter {
super(context, 1, objects);
/* We get the inflator in the constructor */
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view;
/* We inflate the xml which gives us a view */
view = mInflater.inflate(R.layout.my_list_custom_row, parent, false);
/* Get the item in the adapter */
MyObject myObject = getItem(position);
/* Get the widget with id name which is defined in the xml of the row */
TextView name = (TextView) view.findViewById(R.id.name);
/* Populate the row's xml with info from the item */
name.setText(myObject.getName());
/* Return the generated view */
return view;
}
在官方文档中阅读更多信息。
其他回答
该类用于将布局XML文件实例化到相应的View对象中。永远不能直接使用它——使用getLayoutInflater()或getSystemService(String)来检索一个标准的LayoutInflater实例，该实例已经连接到当前上下文，并且为正在运行的设备正确配置了。例如:
LayoutInflater inflater = (LayoutInflater)context.getSystemService
(Context.LAYOUT_INFLATER_SERVICE);
参考:http://developer.android.com/reference/android/view/LayoutInflater.html
膨胀意味着读取描述布局(或GUI元素)的XML文件，并创建与之对应的实际对象，从而使对象在Android应用程序中可见。
final Dialog mDateTimeDialog = new Dialog(MainActivity.this);
// Inflate the root layout
final RelativeLayout mDateTimeDialogView = (RelativeLayout) getLayoutInflater().inflate(R.layout.date_time_dialog, null);
// Grab widget instance
final DateTimePicker mDateTimePicker = (DateTimePicker) mDateTimeDialogView.findViewById(R.id.DateTimePicker);
这个文件可以保存为date_time_dialog.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/DateTimeDialog" android:layout_width="100px"
android:layout_height="wrap_content">
<com.dt.datetimepicker.DateTimePicker
android:id="@+id/DateTimePicker" android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<LinearLayout android:id="@+id/ControlButtons"
android:layout_width="fill_parent" android:layout_height="wrap_content"
android:layout_below="@+id/DateTimePicker"
android:padding="5dip">
<Button android:id="@+id/SetDateTime" android:layout_width="0dip"
android:text="@android:string/ok" android:layout_weight="1"
android:layout_height="wrap_content"
/>
<Button android:id="@+id/ResetDateTime" android:layout_width="0dip"
android:text="Reset" android:layout_weight="1"
android:layout_height="wrap_content"
/>
<Button android:id="@+id/CancelDialog" android:layout_width="0dip"
android:text="@android:string/cancel" android:layout_weight="1"
android:layout_height="wrap_content"
/>
</LinearLayout>
这个文件可以保存为date_time_picker.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="wrap_content" `enter code here`
android:padding="5dip" android:id="@+id/DateTimePicker">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:baselineAligned="true"
android:orientation="horizontal">
<LinearLayout
android:id="@+id/month_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="1dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/month_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/month_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:focusable="false"
android:gravity="center"
android:singleLine="true"
android:textColor="#000000">
</EditText>
<Button
android:id="@+id/month_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/date_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.5dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/date_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/date_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true"/>
<Button
android:id="@+id/date_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/year_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.5dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/year_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/year_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true"/>
<Button
android:id="@+id/year_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/hour_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_marginTop="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/hour_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/hour_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true">
</EditText>
<Button
android:id="@+id/hour_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/min_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.35dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<Button
android:id="@+id/min_plus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_up_final"/>
<EditText
android:id="@+id/min_display"
android:layout_width="45dp"
android:layout_height="35dp"
android:background="@drawable/picker_middle"
android:gravity="center"
android:focusable="false"
android:inputType="number"
android:textColor="#000000"
android:singleLine="true"/>
<Button
android:id="@+id/min_minus"
android:layout_width="45dp"
android:layout_height="45dp"
android:background="@drawable/image_button_down_final"/>
</LinearLayout>
<LinearLayout
android:id="@+id/meridiem_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="0.35dp"
android:layout_marginTop="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:gravity="center"
android:orientation="vertical">
<ToggleButton
android:id="@+id/toggle_display"
style="@style/SpecialToggleButton"
android:layout_width="40dp"
android:layout_height="32dp"
android:layout_marginLeft="5dp"
android:layout_marginTop="45dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="5dp"
android:padding="5dp"
android:gravity="center"
android:textOn="@string/meridiem_AM"
android:textOff="@string/meridiem_PM"
android:checked="true"/>
<!-- android:checked="true" -->
</LinearLayout>
</LinearLayout>
</RelativeLayout>
MainActivity类保存为MainActivity.java:
public class MainActivity extends Activity {
EditText editText;
Button button_click;
public static Activity me = null;
String meridiem;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText = (EditText)findViewById(R.id.edittext1);
button_click = (Button)findViewById(R.id.button1);
button_click.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view){
final Dialog mDateTimeDialog = new Dialog(MainActivity.this);
final RelativeLayout mDateTimeDialogView = (RelativeLayout) getLayoutInflater().inflate(R.layout.date_time_dialog, null);
final DateTimePicker mDateTimePicker = (DateTimePicker) mDateTimeDialogView.findViewById(R.id.DateTimePicker);
// mDateTimePicker.setDateChangedListener();
((Button) mDateTimeDialogView.findViewById(R.id.SetDateTime)).setOnClickListener(new OnClickListener() {
public void onClick(View v) {
mDateTimePicker.clearFocus();
int hour = mDateTimePicker.getHour();
String result_string = mDateTimePicker.getMonth() +" "+ String.valueOf(mDateTimePicker.getDay()) + ", " + String.valueOf(mDateTimePicker.getYear())
+ " " +(mDateTimePicker.getHour()<=9? String.valueOf("0"+mDateTimePicker.getHour()) : String.valueOf(mDateTimePicker.getHour())) + ":" + (mDateTimePicker.getMinute()<=9?String.valueOf("0"+mDateTimePicker.getMinute()):String.valueOf(mDateTimePicker.getMinute()))+" "+mDateTimePicker.getMeridiem();
editText.setText(result_string);
mDateTimeDialog.dismiss();
}
});
// Cancel the dialog when the "Cancel" button is clicked
((Button) mDateTimeDialogView.findViewById(R.id.CancelDialog)).setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
mDateTimeDialog.cancel();
}
});
// Reset Date and Time pickers when the "Reset" button is clicked
((Button) mDateTimeDialogView.findViewById(R.id.ResetDateTime)).setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
mDateTimePicker.reset();
}
});
// Setup TimePicker
// No title on the dialog window
mDateTimeDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
// Set the dialog content view
mDateTimeDialog.setContentView(mDateTimeDialogView);
// Display the dialog
mDateTimeDialog.show();
}
});
}
}
下面是一个示例，用于获取布局的根视图的引用， 膨胀它并使用setContentView(视图视图)
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LayoutInflater li=getLayoutInflater();
View rootView=li.inflate(R.layout.activity_main,null);
setContentView(rootView);
}
Inflater实际上是将数据，视图，实例转换为可见的UI表示.. ..因此，它以编程的方式利用来自适配器等的数据馈送。然后将它与你定义的xml集成，告诉它数据应该如何在UI中表示
Layout inflater是一个读取xml外观描述并将其转换为基于java的View对象的类。
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