我是 Android 编程的新手，总的来说我缺乏编程技能。我一直在关注 Head Start 教程，尽管我知道它在技术上已被删除以进行更新或其他内容。不管怎样，我到了他们只是希望您复制并粘贴代码以使 NASA RSS 提要和 Android 应用程序相互通信的部分，但由于某些或其他原因没有任何显示。我只是得到一个白屏，并且 logcat 错误似乎对我所看到的其他应用程序没有太大影响。我使用的测试数据有效，所以我认为 xml 很好，所以也许是我的 Java。我似乎找不到任何东西。任何人都可以看到我做错了什么。整个周末都在努力。这可能是复制粘贴的代码，但我不明白。
package love.android.nasadailyimage;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ImageView;
import android.widget.TextView;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.jar.Attributes;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
public class NasaDailyImage extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_nasa_daily_image);
IotdHandler handler = new IotdHandler();
handler.processFeed();
resetDisplay(handler.getTitle(), handler.getDate(), handler.getImage(), handler.getDescription());
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_nasa_daily_image, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public class IotdHandler extends DefaultHandler {
private String url = "http://www.nasa.gov/rss/dyn/image_of_the_day.rss";
private boolean inUrl = false;
private boolean inTitle = false;
private boolean inDescription = false;
private boolean inItem = false;
private boolean inDate = false;
private Bitmap image = null;
private String title = null;
private StringBuffer description = null;
private String date = null;
public void processFeed() {
try {
SAXParserFactory factory =
SAXParserFactory.newInstance();
SAXParser parser = factory.newSAXParser();
XMLReader reader = parser.getXMLReader();
reader.setContentHandler(this);
InputStream inputStream = new URL(url).openStream();
reader.parse(new InputSource(inputStream));
} catch (Exception e) {
}
}
private Bitmap getBitmap(String url) {
try {
HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
connection.setDoInput(true);
connection.connect();
InputStream input = connection.getInputStream();
Bitmap bitmap = BitmapFactory.decodeStream(input);
input.close();
return bitmap;
} catch (IOException ioe) {
return null;
}
}
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
if (localName.equals("url")) {
inUrl = true;
} else {
inUrl = false;
}
if (localName.startsWith("item")) {
inItem = true;
} else if (inItem) {
if (localName.equals("title")) {
inTitle = true;
} else {
inTitle = false;
}
if (localName.equals("description")) {
inDescription = true;
} else {
inDescription = false;
}
if (localName.equals("pubDate")) {
inDate = true;
} else {
inDate = false;
}
}
}
public void characters(char ch[], int start, int length) {
String chars = new String(ch).substring(start, start + length);
if (inUrl && url == null) {
image = getBitmap(chars);
}
if (inTitle && title == null) {
title = chars;
}
if (inDescription) {
description.append(chars);
}
if (inDate && date == null) {
date = chars;
}
}
public Bitmap getImage() {
return image;
}
public String getTitle() {
return title;
}
public StringBuffer getDescription() {
return description;
}
public String getDate() {
return date;
}
}
private void resetDisplay(String title, String date, Bitmap image, StringBuffer description){
TextView titleView = (TextView) findViewById(R.id.imageTitle);
titleView.setText(title);
TextView dateView = (TextView) findViewById(R.id.imageDate);
dateView.setText(date);
ImageView imageView = (ImageView) findViewById(R.id.imageDisplay);
imageView.setImageBitmap(image);/////////////////////////////////////////
TextView descriptionView = (TextView) findViewById(R.id.imageDescription);
descriptionView.setText(description);
}
}
XML 以防有帮助
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".NasaDailyImage">
<TextView
android:id="@+id/imageTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/image_title" />
<TextView
android:id="@+id/imageDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/image_date" />
<ImageView
android:id="@+id/imageDisplay"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:src="@mipmap/galaxy"
android:scaleType="fitXY"
android:adjustViewBounds="true"/>
<TextView
android:id="@+id/imageDescription"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/image_description" />
</LinearLayout>
</ScrollView>
任何帮助将不胜感激。我会问这里的人，但在我的国家“纳米比亚”，很少有人能接触到我能接触到的 android 编程。
我的 S4 设备上的 LogCat
04-20 11:07:17.204 25660-25660/love.android.nasadailyimage W/IInputConnectionWrapper﹕ getExtractedText on inactive InputConnection
04-20 11:07:17.204 25660-25660/love.android.nasadailyimage W/IInputConnectionWrapper﹕ getTextBeforeCursor on inactive InputConnection
04-20 11:07:17.209 25660-25660/love.android.nasadailyimage W/IInputConnectionWrapper﹕ getSelectedText on inactive InputConnection
04-20 11:07:17.209 25660-25660/love.android.nasadailyimage W/IInputConnectionWrapper﹕ getTextAfterCursor on inactive InputConnection
04-20 11:12:38.244 25660-25660/love.android.nasadailyimage W/IInputConnectionWrapper﹕ getExtractedText on inactive InputConnection
04-20 11:12:38.244 25660-25660/love.android.nasadailyimage W/IInputConnectionWrapper﹕ getTextBeforeCursor on inactive InputConnection
04-20 11:12:38.244 25660-25660/love.android.nasadailyimage W/IInputConnectionWrapper﹕ getSelectedText on inactive InputConnection
04-20 11:12:38.249 25660-25660/love.android.nasadailyimage W/IInputConnectionWrapper﹕ getTextAfterCursor on inactive InputConnection
04-20 11:16:06.154 30742-30742/love.android.nasadailyimage W/ApplicationPackageManager﹕ getCSCPackageItemText()
04-20 11:16:06.154 30742-30742/love.android.nasadailyimage I/PersonaManager﹕ getPersonaService() name persona_policy
04-20 11:16:06.229 30742-30742/love.android.nasadailyimage I/dalvikvm﹕ Could not find method android.view.ViewGroup.onNestedScrollAccepted, referenced from method android.support.v7.internal.widget.ActionBarOverlayLayout.onNestedScrollAccepted
04-20 11:16:06.229 30742-30742/love.android.nasadailyimage W/dalvikvm﹕ VFY: unable to resolve virtual method 12208: Landroid/view/ViewGroup;.onNestedScrollAccepted (Landroid/view/View;Landroid/view/View;I)V
04-20 11:16:06.229 30742-30742/love.android.nasadailyimage D/dalvikvm﹕ VFY: replacing opcode 0x6f at 0x0000
04-20 11:16:06.229 30742-30742/love.android.nasadailyimage I/dalvikvm﹕ Could not find method android.view.ViewGroup.onStopNestedScroll, referenced from method android.support.v7.internal.widget.ActionBarOverlayLayout.onStopNestedScroll
04-20 11:16:06.229 30742-30742/love.android.nasadailyimage W/dalvikvm﹕ VFY: unable to resolve virtual method 12214: Landroid/view/ViewGroup;.onStopNestedScroll (Landroid/view/View;)V
04-20 11:16:06.229 30742-30742/love.android.nasadailyimage D/dalvikvm﹕ VFY: replacing opcode 0x6f at 0x0000
04-20 11:16:06.234 30742-30742/love.android.nasadailyimage I/dalvikvm﹕ Could not find method android.support.v7.internal.widget.ActionBarOverlayLayout.stopNestedScroll, referenced from method android.support.v7.internal.widget.ActionBarOverlayLayout.setHideOnContentScrollEnabled
04-20 11:16:06.234 30742-30742/love.android.nasadailyimage W/dalvikvm﹕ VFY: unable to resolve virtual method 9779: Landroid/support/v7/internal/widget/ActionBarOverlayLayout;.stopNestedScroll ()V
04-20 11:16:06.234 30742-30742/love.android.nasadailyimage D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x000e
04-20 11:16:06.244 30742-30742/love.android.nasadailyimage I/dalvikvm﹕ Could not find method android.content.res.TypedArray.getChangingConfigurations, referenced from method android.support.v7.internal.widget.TintTypedArray.getChangingConfigurations
04-20 11:16:06.244 30742-30742/love.android.nasadailyimage W/dalvikvm﹕ VFY: unable to resolve virtual method 392: Landroid/content/res/TypedArray;.getChangingConfigurations ()I
04-20 11:16:06.244 30742-30742/love.android.nasadailyimage D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
04-20 11:16:06.244 30742-30742/love.android.nasadailyimage I/dalvikvm﹕ Could not find method android.content.res.TypedArray.getType, referenced from method android.support.v7.internal.widget.TintTypedArray.getType
04-20 11:16:06.244 30742-30742/love.android.nasadailyimage W/dalvikvm﹕ VFY: unable to resolve virtual method 414: Landroid/content/res/TypedArray;.getType (I)I
04-20 11:16:06.244 30742-30742/love.android.nasadailyimage D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
04-20 11:16:06.244 30742-30742/love.android.nasadailyimage I/dalvikvm﹕ Could not find method android.content.res.Resources.getDrawable, referenced from method android.support.v7.internal.widget.ResourcesWrapper.getDrawable
04-20 11:16:06.249 30742-30742/love.android.nasadailyimage W/dalvikvm﹕ VFY: unable to resolve virtual method 355: Landroid/content/res/Resources;.getDrawable (ILandroid/content/res/Resources$Theme;)Landroid/graphics/drawable/Drawable;
04-20 11:16:06.249 30742-30742/love.android.nasadailyimage D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
04-20 11:16:06.249 30742-30742/love.android.nasadailyimage I/dalvikvm﹕ Could not find method android.content.res.Resources.getDrawableForDensity, referenced from method android.support.v7.internal.widget.ResourcesWrapper.getDrawableForDensity
04-20 11:16:06.249 30742-30742/love.android.nasadailyimage W/dalvikvm﹕ VFY: unable to resolve virtual method 357: Landroid/content/res/Resources;.getDrawableForDensity (IILandroid/content/res/Resources$Theme;)Landroid/graphics/drawable/Drawable;
04-20 11:16:06.249 30742-30742/love.android.nasadailyimage D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
04-20 11:16:06.369 30742-30742/love.android.nasadailyimage D/dalvikvm﹕ GC_FOR_ALLOC freed 130K, 6% free 16994K/18052K, paused 15ms, total 15ms
04-20 11:16:06.389 30742-30742/love.android.nasadailyimage I/dalvikvm-heap﹕ Grow heap (frag case) to 28.887MB for 11943952-byte allocation
04-20 11:16:06.404 30742-30751/love.android.nasadailyimage D/dalvikvm﹕ GC_FOR_ALLOC freed 4K, 4% free 28654K/29720K, paused 12ms, total 12ms
04-20 11:16:06.479 30742-30742/love.android.nasadailyimage I/System.out﹕ main(HTTPLog):SmartBonding Enabling is false, log to file is false, DBG is false
04-20 11:16:06.594 30742-30742/love.android.nasadailyimage D/OpenGLRenderer﹕ Enabling debug mode 0
AndroidManifest 请求
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="love.android.nasadailyimage" >
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".NasaDailyImage"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-permission android:name="android.permission.INTERNET"/>
</manifest>
构建.gradle
apply plugin: 'com.android.application'
android {
compileSdkVersion 21
buildToolsVersion "21.1.2"
defaultConfig {
applicationId "love.android.nasadailyimage"
minSdkVersion 11
targetSdkVersion 21
versionCode 1
versionName "1.0"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:22.0.0'
}
编辑:添加了我的 LogCat 和我的 AndroidManifest
最佳答案
在 StackOverflow 上发现了一个问题，该问题遵循与您相同的教程。也许这对你有帮助
Android Head First "NASA daily image App"
如前所述，您应该使用 AsyncTask，并在请求返回时处理请求 (onPostExecute)。您的代码的问题是，您发送了一个请求，并且在您调用 resetDisplay 之后，响应还没有返回...这就是您看到空白屏幕的原因。
关于java - 无法让 Android Tutorial 工作，初级程序员，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/29744861/