将 json 文件保存到内部存储器，然后稍后调用该文件 [英] saving a json file to internal memory then calling that file later
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问题描述
我有一个 json 文件，我试图在单击 btn 时保存一个，然后另一个 btn 将在 textview 中显示解码的 json 文件
I have a json file I'm trying to save when btn one is clicked and then another btn that will display the decoded json file in a textview
public class MainActivity extends Activity {
/** Called when the activity is first created. */
String result = "";
InputStream is = null;
TextView one = (TextView) findViewById(R.id.showView);
HttpEntity entity = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//pulls a file from my server then saves it
Button btn1 = (Button) findViewById(R.id.downloadBtn);
btn1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
saveJson();
//end of onClick
}
//end of onClickListener
});
//should show the saved file
Button btn2 = (Button) findViewById(R.id.showBtn);
btn2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
showJson();
//end of onClick
}
//end of onClickListener
});
//end of oncreate()
}
public void saveJson(){
TextView one = (TextView) findViewById(R.id.showView);
try{
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost("http://10.0.2.2/textures_story_list.php");
HttpResponse response = httpClient.execute(httpPost);
entity = response.getEntity();
//from here what do i need to add to save the file as .json
}catch(Exception e) {
one.setText("error3");
}
//end of returnJson()
}
public void showJson(){
//from here what should i have to show the file story_list.json
try{
is = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "
");
}
is.close();
result = sb.toString();
}catch(Exception e) {
}
try{
JSONArray jArray = new JSONArray(result);
String storyNames = "";
for(int i = 0;i<jArray.length();i++){
storyNames += jArray.getJSONObject(i).getString("story_name") + "
";
}
one.setText(storyNames);
}
catch(JSONException e) {
}
return;
//end of returnJson()
}
//end of class body
}
它在启动时崩溃_
runtimeExecption unable to instatiate activity ComponentInfo nullpointer
好的，这里解决的问题是我添加的代码以保存然后显示文件
oK that problem fixed here is the codes I added to save and then show the file
public class MainActivity extends Activity {
/** Called when the activity is first created. */
String result = "";
InputStream is = null;
HttpEntity entity = null;
HttpEntity readString = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//pulls a file from my server then saves it
Button btn1 = (Button) findViewById(R.id.downloadBtn);
btn1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
saveJson();
//end of onClick
}
//end of onClickListener
});
//should show the saved file
Button btn2 = (Button) findViewById(R.id.showBtn);
btn2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
showJson();
//end of onClick
}
//end of onClickListener
});
//end of oncreate()
}
public void saveJson(){
TextView one = (TextView) findViewById(R.id.showView);
try{
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost("http://10.0.2.2/textures_story_list.php");
HttpResponse response = httpClient.execute(httpPost);
entity = response.getEntity();
//from here what do i need to add to save the file as .json
}catch(Exception e) {
one.setText("error3");
}
try{
HttpEntity text = entity;
FileOutputStream fOut = openFileOutput("story.json",MODE_WORLD_READABLE);
OutputStreamWriter osw = new OutputStreamWriter(fOut);
osw.write(text);
osw.flush();
osw.close();
}catch(IOException ioe){
}
//end of returnJson()
}
public void showJson(){
//from here what should i have to show the file story_list.json
try{
FileInputStream fIn = openFileInput("story.json");
InputStreamReader isr = new InputStreamReader(fIn);
char[] inputBuffer = new char[11];
//len is the length of that saved string in the file
isr.read(inputBuffer);
// String readString = new String(inputBuffer);
isr = readString.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "
");
}
is.close();
result = sb.toString();
}catch(Exception e) {
}
try{
JSONArray jArray = new JSONArray(result);
String storyNames = "";
for(int i = 0;i<jArray.length();i++){
storyNames += jArray.getJSONObject(i).getString("story_name") + "
";
}
TextView one = (TextView) findViewById(R.id.showView);
one.setText(storyNames);
}
catch(JSONException e) {
}
return;
//end of returnJson()
}
//end of class body
}
有人可以帮我解决错误或告诉我我做错了什么吗?
Can someone help me fix the errors or tell me what I'm doing wrong?
推荐答案
两个建议:
1) 将此分配移动到您的 onCreate() 方法中:
1) Move this assignment into your onCreate() method:
one = (TextView) findViewById(R.id.showView);
2) 如果您仍然有问题，请逐步检查您的代码以确定您尝试取消引用空指针的确切位置.我猜这可能是您的findViewById()"调用之一.
2) If you still have the problem, then step through your code to determine exactly where you're trying to dereference a null pointer. I'm guessing it's probably one of your "findViewById()" calls.
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