Android 在倒计时';中更改布局时获取nullPointerException;s finish()方法
我在上收到一个nullPointerException “button.setOnClickListener(this);”…在中更改布局时 CountDownTimer的finish()方法。这是代码…请帮我解决这个问题。。。。。。。提前谢谢Android 在倒计时';中更改布局时获取nullPointerException;s finish()方法,android,nullpointerexception,Android,Nullpointerexception,我在上收到一个nullPointerException “button.setOnClickListener(this);”…在中更改布局时 CountDownTimer的finish()方法。这是代码…请帮我解决这个问题。。。。。。。提前谢谢 package com.example.vikrant.countdowntimer; import android.content.Context; import android.graphics.Bitmap; import android.gra
package com.example.vikrant.countdowntimer;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.CountDownTimer;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Layout;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.concurrent.ExecutionException;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
Button button;
ImageView image;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final Context c = getApplicationContext();
new CountDownTimer(10000,5000){
@Override
public void onTick(long millisUntilFinished) {
setContentView(R.layout.timer);
}
@Override
public void onFinish() {
setContentView(R.layout.activity_main);
}
}.start();
button = (Button) findViewById(R.id.button);
button.setOnClickListener(this);
}
@Override
public void onClick(View v) {
String url="https://firebasestorage.googleapis.com/v0/b/fir-assignment-34e5b.appspot.com/o/rangoliA%2Frangolinew.jpg?alt=media&token=4a376937-7fec-420a-a18c-8c9ec7da95af";
image = (ImageView) findViewById(R.id.imageView);
DownloadImage downloadImage = new DownloadImage();
Bitmap bitmap;
try {
bitmap = downloadImage.execute(url).get();
image.setImageBitmap(bitmap);
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
public class DownloadImage extends AsyncTask<String,Void,Bitmap>{
@Override
protected Bitmap doInBackground(String... params) {
URL url;
HttpURLConnection httpURLConnection;
try {
url = new URL(params[0]);
httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.connect();
InputStream inputStream = httpURLConnection.getInputStream();
Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
return bitmap;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}
}
package com.example.vikrant.countdowntimer;
导入android.content.Context;
导入android.graphics.Bitmap;
导入android.graphics.BitmapFactory;
导入android.os.AsyncTask;
导入android.os.CountDownTimer;
导入android.support.v7.app.AppActivity;
导入android.os.Bundle;
导入android.text.Layout;
导入android.view.LayoutInflater;
导入android.view.view;
导入android.widget.Button;
导入android.widget.ImageView;
导入java.io.IOException;
导入java.io.InputStream;
导入java.net.HttpURLConnection;
导入java.net.MalformedURLException;
导入java.net.URL;
导入java.util.concurrent.ExecutionException;
公共类MainActivity扩展AppCompatActivity实现View.OnClickListener{
按钮;
图像视图图像;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
最终上下文c=getApplicationContext();
新倒计时(100005000){
@凌驾
公共void onTick(长毫秒未完成){
setContentView(R.layout.timer);
}
@凌驾
公共无效onFinish(){
setContentView(R.layout.activity_main);
}
}.start();
按钮=(按钮)findViewById(R.id.button);
setOnClickListener(此);
}
@凌驾
公共void onClick(视图v){
字符串url=”https://firebasestorage.googleapis.com/v0/b/fir-assignment-34e5b.appspot.com/o/rangoliA%2Frangolinew.jpg?alt=media&token=4a376937-7fec-420a-a18c-8c9ec7da95af”;
image=(ImageView)findViewById(R.id.ImageView);
DownloadImage DownloadImage=新的DownloadImage();
位图;
试一试{
位图=downloadImage.execute(url.get();
setImageBitmap(位图);
}捕捉(中断异常e){
e、 printStackTrace();
}捕获(执行例外){
e、 printStackTrace();
}
}
公共类DownloadImage扩展异步任务{
@凌驾
受保护位图doInBackground(字符串…参数){
网址;
HttpURLConnection HttpURLConnection;
试一试{
url=新url(参数[0]);
httpURLConnection=(httpURLConnection)url.openConnection();
httpURLConnection.connect();
InputStream InputStream=httpURLConnection.getInputStream();
位图位图=位图工厂.decodeStream(inputStream);
返回位图;
}捕获(例外e){
e、 printStackTrace();
返回null;
}
}
}
}
您的按钮可能在“R.layout.activity\u main”中定义。设置其他内容时,“findViewById(R.id.button)”将返回null(因为它未在其他布局中定义)
毕竟,为什么要更改布局?计时器布局/活动\u主布局中是否有此按钮?在完成计时器之前,只需检查条件。否此按钮位于activity_main.xml中。您是否试图在android中制作一个splsh屏幕?是的,按钮是在activity_main.xml中定义的……我想在我的应用程序启动时自动更改布局……是否有任何方法可以避免出现此异常并执行我想要的操作??你是说android中的splsh屏幕?