java - 实现图像淡入时基本应用程序崩溃

Question

我正在尝试开发一个简单的第一个 Android 应用程序，虽然最终它将是一个摇动激活的应用程序，但现在它仍然可以通过单击按钮来工作，因为我需要能够测试它在我拥有的模拟器上。

该应用程序的最终目标是，当设备摇晃时，从三个随机数字中选择一个(每个数字对应于节目中的一个角色)并读取该数字以淡入该角色的图像。紧接着，它会淡入来自该特定字符的引号数组中的随机引号。

目前，我已经让应用程序正常工作，当我单击按钮时，应用程序选择一个字符，并从该字符的数组中选择一个引号，并且能够淡入该引号。为了实现图像淡入，我做了一些让应用程序在我尝试运行时崩溃的事情。

我确信这会是一些愚蠢的错误，但如果能找到它那就太好了。

该项目有四个类文件:MainActivity.java、DoctorWho.java、Nine.java、Ten.java 和 >11.java。九、十和十一几乎完全相同，只是使用不同的引号。

在尝试添加图像淡入时，我将其添加到DoctorWho.java，此处:

public class DoctorWho {

private Nine mNine = new Nine();
private Ten mTen = new Ten();
private Eleven mEleven = new Eleven();
private ImageView mImageView1;
private ImageView mImageView2;
private ImageView mImageView3;

int randomNumber = 0;

public String getDoctorQuote() {
    String quote = "";

    // Choose a Random number out of three values
    Random randomGenerator = new Random();
    int randomNumber = randomGenerator.nextInt(3);

    // Use that value to choose which of the Doctors to get a quote from
    if (randomNumber == 0) {
        // Quote from Nine
        quote = mNine.getQuote();
    }
    else if (randomNumber == 1) {
        // Quote from Ten
        quote = mTen.getQuote();
    }
    else if (randomNumber == 2) {
        // Quote from Eleven
        quote = mEleven.getQuote();
    }
    else {
        quote = "Error";
    }
    return quote;
}

public void animateDoctor() {
    if (randomNumber == 0) {
        animateNinthDoctor();
    }
    else if (randomNumber == 1) {
        animateTenthDoctor();
    }
    else if (randomNumber == 2) {
        animateEleventhDoctor();
    }
}

private void animateNinthDoctor() {
    AlphaAnimation fadeInAnimation = new AlphaAnimation(0, 1);
    fadeInAnimation.setDuration(1500);
    fadeInAnimation.setFillAfter(true);
    mImageView1.setAnimation(fadeInAnimation);
}

private void animateTenthDoctor() {
    AlphaAnimation fadeInAnimation = new AlphaAnimation(0, 1);
    fadeInAnimation.setDuration(1500);
    fadeInAnimation.setFillAfter(true);
    mImageView2.setAnimation(fadeInAnimation);
}

private void animateEleventhDoctor() {
    AlphaAnimation fadeInAnimation = new AlphaAnimation(0, 1);
    fadeInAnimation.setDuration(1500);
    fadeInAnimation.setFillAfter(true);
    mImageView3.setAnimation(fadeInAnimation);
}

在我的 MainActivity.java 文件中，我尝试在此处单击运行动画:

            @Override
        public void onClick(View arg0) {
            String quote = mDoctorWho.getDoctorQuote();
            mDoctorWho.animateDoctor();
            // mQuoteLabel is the TextView where the quotes are displayed
            mQuoteLabel.setText(quote);
            animateQuoteIn();   
        }

该应用程序仍然可以正常启动，并且在模拟器上运行它之前不会显示任何错误。当我单击应该运行此序列的按钮时，应用程序崩溃了。控制台中没有显示任何错误，并且我无法在 LogCat View 中找到特定行 - 但我可能找错了地方。让我知道用更多代码更新帖子是否有助于查找导致崩溃的原因。

Answer 1

尝试按如下方式更改 DoctorWho 类:

你还初始化了DoctorWho类中的mImageView1，mImageView2，mImageView3吗？？？

public class DoctorWho {

private Nine mNine = new Nine();
private Ten mTen = new Ten();
private Eleven mEleven = new Eleven();
private ImageView mImageView1;
private ImageView mImageView2;
private ImageView mImageView3;

int randomNumber = 0;

public String getDoctorQuote() {
    String quote = "";

    // Choose a Random number out of three values
    Random randomGenerator = new Random();
    randomNumber = randomGenerator.nextInt(3);//<--- don't create new randonNumber 

    // Use that value to choose which of the Doctors to get a quote from
    if (randomNumber == 0) {
        // Quote from Nine
        quote = mNine.getQuote();
    }
    else if (randomNumber == 1) {
        // Quote from Ten
        quote = mTen.getQuote();
    }
    else if (randomNumber == 2) {
        // Quote from Eleven
        quote = mEleven.getQuote();
    }
    else {
        quote = "Error";
    }
    return quote;
}

public void animateDoctor() {
    ImageView imageView=null;
    if (randomNumber == 0) {
        imageView=mImageView1;
    }
    else if (randomNumber == 1) {
         imageView=mImageView2;
    }
    else if (randomNumber == 2) {
         imageView=mImageView3;
    }

    AlphaAnimation fadeInAnimation = new AlphaAnimation(0, 1);
    fadeInAnimation.setDuration(1500);
    fadeInAnimation.setFillAfter(true);
    imageView.setAnimation(fadeInAnimation);
}

}