了解getIntExtra（）参数
@Overrideprotected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_details);$$
// pull the turtle's ID out of the intent that the MainActivity used to load me
Intent intent = getIntent();
int id = intent.getIntExtra("turtle_id", R.id.leo);
String text = "";
if (id == R.id.leo) {
text = TURTLE_DETAILS[0];
} else if (id == R.id.mike) {
text = TURTLE_DETAILS[1];
} else if (id == R.id.don) {
text = TURTLE_DETAILS[2];
} else { // if (id == R.id.raph)
text = TURTLE_DETAILS[3];
}
我无法解决问题
int id = intent.getIntExtra("turtle_id", R.id.leo);我看不到为什么R.id.leo被指定？turtle_id是名称，但我不确定R.id.leo。
的片段 MainActivity.java
/* * Called when the Details activity finishes running and comes back to here.
*/
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
}
/*
* Called when the user clicks on the large TMNT image button.
* Loads the DetailsActivity for more information about that turtle.
*/
public void onClickTurtleImage(View view) {
Intent intent = new Intent(this, DetailsActivity.class);
RadioGroup group = (RadioGroup) findViewById(R.id.turtle_group);
int id = group.getCheckedRadioButtonId();
intent.putExtra("turtle_id", id);
startActivity(intent);
}
/*
* This method is called when the user chooses one of the turtle radio buttons.
* In this code we set which turtle image is visible on the screen in the ImageView.
*/
public void pickTurtle(View view) {
ImageButton img = (ImageButton) findViewById(R.id.turtle);
if (view.getId() == R.id.leo) {
img.setImageResource(R.drawable.tmntleo);
} else if (view.getId() == R.id.mike) {
img.setImageResource(R.drawable.tmntmike);
} else if (view.getId() == R.id.don) {
img.setImageResource(R.drawable.tmntdon);
} else if (view.getId() == R.id.raph) {
img.setImageResource(R.drawable.tmntraph);
}
}
}
DetailsActivity.java
/* * CS 193A, Winter 2015, Marty Stepp
* This app is a continuation of our TMNT app from last week.
* Today's version adds a second activity and launches that activity using an Intent.
* This file represents the Java code for the second activity.
*/
package com.example.stepp.layoutfun;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
public class DetailsActivity extends Activity {
/*
* Constant array of data about each of the four turtles.
* (This is not the most idiomatic way to store such information,
* but we'll come back to it later.)
*/
private static final String[] TURTLE_DETAILS = {
""/*Long Story but not relevant for the question*/
};
/*
* Called when the activity first gets created.
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_details);
// pull the turtle's ID out of the intent that the MainActivity used to load me
Intent intent = getIntent();
int id = intent.getIntExtra("turtle_id", R.id.leo);
String text = "";
if (id == R.id.leo) {
text = TURTLE_DETAILS[0];
} else if (id == R.id.mike) {
text = TURTLE_DETAILS[1];
} else if (id == R.id.don) {
text = TURTLE_DETAILS[2];
} else { // if (id == R.id.raph)
text = TURTLE_DETAILS[3];
}
TextView tv = (TextView) findViewById(R.id.turtle_info);
tv.setText(text);
}
}
activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:gravity="top|center"
android:orientation="vertical"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
<RadioGroup
android:id="@+id/turtle_group"
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<RadioButton
android:id="@+id/leo"
android:onClick="pickTurtle"
android:text="Leo"
android:checked="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<RadioButton
android:id="@+id/mike"
android:onClick="pickTurtle"
android:text="Mike"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<RadioButton
android:id="@+id/don"
android:onClick="pickTurtle"
android:text="Don"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<RadioButton
android:id="@+id/raph"
android:onClick="pickTurtle"
android:text="Raph"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RadioGroup>
<ImageButton
android:id="@+id/turtle"
android:onClick="onClickTurtleImage"
android:src="@drawable/tmntleo"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
二手教程在这里。
回答：
该方法的文档getIntExtra如下：
从意图中检索扩展数据。
name所需项目的名称。
defaultValue如果没有使用给定名称存储所需类型的值，则返回该值。以前使用putExtra（）添加的项目的值；如果未找到，则为默认值。
因此，在您的示例中，如果该键存在于中，则将被分配id与该键关联的整数值；如果不turtle_id存在Intent，则将被分配该整数值R.id.leo。通常，使用此方法是为了在使用者启动this时未能传递必需的信息时提供合理的默认值Activity。在您的特定情况下，此行为可以解释为：“如果呼叫者在启动此操作时忘记告诉我选择了哪只乌龟Activity，则假定是狮子座。”
以上是 了解getIntExtra（）参数 的全部内容， 来源链接： utcz.com/qa/415821.html
