java setImageResource在Android中不工作

Question

我是java的初学者，我想随机化一些图片，我用这段代码来实现

int[] cards = {R.drawable.i1, R.drawable.i2, R.drawable.i3};
Random n = new Random();
Resources resources = getResources();
imgRandom.setImageResource(cards[n]);

而且它不起作用，因为setImageResource是红色的，Android Studio说：无法解析符号“setImageResource”。有人能帮我吗

所有java代码：

    package eduard.alarmamotivationala;

import 安卓.content.res.Resources;
import 安卓.support.v7.app.AppCompatActivity;
import 安卓.os.Bundle;
import 安卓.widget.ImageView;

import java.util.Random;

public class MainActivity extends AppCompatActivity {

    ImageView m_imgRandom;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public ImageView getM_imgRandom() { int[] cards = {R.drawable.i1, R.drawable.i2, R.drawable.i3};
        Random n = new Random();
        Resources resources = getResources();
        m_imgRandom.setImageResource(cards [3]);
        return m_imgRandom; }
}

所有XML代码：

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
    xmlns:tools="http://schemas.安卓.com/tools"
    安卓:id="@+id/activity_main"
    安卓:layout_width="match_parent"
    安卓:layout_height="match_parent"
    安卓:paddingBottom="@dimen/activity_vertical_margin"
    安卓:paddingLeft="@dimen/activity_horizontal_margin"
    安卓:paddingRight="@dimen/activity_horizontal_margin"
    安卓:paddingTop="@dimen/activity_vertical_margin"
    安卓:background="#000000"
    tools:context="eduard.alarmamotivationala.MainActivity">

    <Button
        安卓:text="Porneste alarma"
        安卓:layout_width="wrap_content"
        安卓:layout_height="wrap_content"
        安卓:layout_alignParentTop="true"
        安卓:layout_alignParentStart="true"
        安卓:id="@+id/button" />

    <Button
        安卓:text="Opreste alarma"
        安卓:layout_width="wrap_content"
        安卓:layout_height="wrap_content"
        安卓:layout_alignParentTop="true"
        安卓:layout_alignParentEnd="true"
        安卓:id="@+id/button2" />

    <TextView
        安卓:text="Inca nu ai setat alarma"
        安卓:textColor="#FFFFFF"
        安卓:layout_width="wrap_content"
        安卓:layout_height="wrap_content"
        安卓:layout_below="@+id/button"
        安卓:layout_centerHorizontal="true"
        安卓:layout_marginTop="11dp"
        安卓:id="@+id/textView" />

    <TimePicker
        安卓:layout_width="wrap_content"
        安卓:layout_height="wrap_content"
        安卓:scaleX="0.7"
        安卓:scaleY="0.7"
        安卓:headerBackground="@安卓:color/transparent"
        安卓:numbersSelectorColor="#027aed"
        安卓:id="@+id/timePicker"
        安卓:layout_marginTop="36dp"
        安卓:layout_alignParentTop="true"
        安卓:layout_alignParentStart="true" />

    <ImageView
        安卓:id="@+id/imgRandom"
        安卓:layout_width="wrap_content"
        安卓:layout_height="wrap_content"
        安卓:scaleType = "centerCrop" />
</RelativeLayout>

Answer 1

int[] cards = {R.drawable.i1, R.drawable.i2, R.drawable.i3};
int n = new Random().nextInt(3);
imgRandom.setImageResource(cards[n]);

生成从0到2的随机数

int n = new Random().nextInt(3);

从数组中取出随机图像并设置为image

imgRandom.setImageResource(cards[n]);

就这些

Answer 2

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:background="#000000"
    tools:context="eduard.alarmamotivationala.MainActivity">

    <Button
        android:text="Porneste alarma"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true"
        android:id="@+id/button" />

    <Button
        android:text="Opreste alarma"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_alignParentEnd="true"
        android:id="@+id/button2" />

    <TextView
        android:text="Inca nu ai setat alarma"
        android:textColor="#FFFFFF"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/button"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="11dp"
        android:id="@+id/textView" />

    <TimePicker
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:scaleX="0.7"
        android:scaleY="0.7"
        android:headerBackground="@android:color/transparent"
        android:numbersSelectorColor="#027aed"
        android:id="@+id/timePicker"
        android:layout_marginTop="36dp"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true" />

    <! changed wrap_content to match_parent for getting the full screen image view >

    <ImageView
        android:id="@+id/imgRandom"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType = "centerCrop" />
</RelativeLayout>

也试试看

android:scaleType = "centerInside"

及

android:scaleType = "fitXY"

感受变化

在java文件中

    package eduard.alarmamotivationala;

import android.content.res.Resources;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;

import java.util.Random;

public class MainActivity extends AppCompatActivity {

    int[] cards = {R.drawable.i1, R.drawable.i2, R.drawable.i3};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //   initializing the image view
        ImageView m_imgRandom = (ImageView) findViewById(R.id.imgRandom);
        //   choosing a random number from 0 to 2
        int n = new Random().nextInt(3);
        //   choosing the random image from cards array using the random number
        m_imgRandom.setImageResource(cards[n]);

    }
}

没有测试。希望它能奏效