Question

我有问题是“java.lang.NullPointerException” 我想知道如何解决它，我想要表现出来看看图片我有两个类MainActivity和MaterialDialog 请参阅错误消息：

> FATAL EXCEPTION: main                                                 
> Process: com.example.android.dialoge, PID: 14884                      
> java.lang.NullPointerException                                        
> at
> com.example.android.dialoge.MaterialDialog$Builder.setTitle(MaterialDialog.java:265)
> at
> com.example.android.dialoge.MaterialDialog$Builder.<init>(MaterialDialog.java:198)
> at
> com.example.android.dialoge.MaterialDialog$Builder.<init>(MaterialDialog.java:179)
> at
> com.example.android.dialoge.MaterialDialog.show(MaterialDialog.java:59)
> at com.example.android.dialoge.MainActivity.test(MainActivity.java:58)
> at
> com.example.android.dialoge.MainActivity$1.onClick(MainActivity.java:28)
> at android.view.View.performClick(View.java:4438)                     
> at android.view.View$PerformClick.run(View.java:18422)                
> at android.os.Handler.handleCallback(Handler.java:733)                
> at android.os.Handler.dispatchMessage(Handler.java:95)                
> at android.os.Looper.loop(Looper.java:136)                            
> at android.app.ActivityThread.main(ActivityThread.java:5001)          
> at java.lang.reflect.Method.invokeNative(Native Method)               
> at java.lang.reflect.Method.invoke(Method.java:515)                   
> at
> com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
> at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)       
> at dalvik.system.NativeStart.main(Native Method)

//查看第一堂课MainActivity

import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;

public class MainActivity extends Activity {
    Button clickButton;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        clickButton = (Button) findViewById(R.id.button);
        clickButton.setOnClickListener( new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                test();
            }
                /*
                MaterialDialog dialog = new MaterialDialog.Builder(MainActivity.this).build();
                RecyclerView list = dialog.getRecyclerView();
                 // Do something with it
                dialog.show();
                */
        });
    }
    void test(){
        final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1);
        for (int j = 0; j < 38; j++) {

            arrayAdapter.add("This is item " + j);
        }
        ListView listView = new ListView(this);
        listView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.MATCH_PARENT));
        float scale = getResources().getDisplayMetrics().density;
        int dpAsPixels = (int) (8 * scale + 0.5f);
        listView.setPadding(0, dpAsPixels, 0, dpAsPixels);
        listView.setDividerHeight(0);
        listView.setAdapter(arrayAdapter);
        final com.example.android.dialoge.MaterialDialog alert = new com.example.android.dialoge.MaterialDialog(this)
        .setTitle("ghjghj").setContentView(listView);
        alert.setPositiveButton("OK", new View.OnClickListener() {
            @Override public void onClick(View v) {
                alert.dismiss();
            }
        });
        alert.show();
    }
 }

//参见Second Class MaterialDialog：

public class MaterialDialog {

    private final static int BUTTON_BOTTOM = 9;
    private final static int BUTTON_TOP = 9;

    private boolean mCancel;
    private Context mContext;
    private AlertDialog mAlertDialog;
    private MaterialDialog.Builder mBuilder;
    private View mView;
    private int mTitleResId;
    private CharSequence mTitle;
    private int mMessageResId;
    private CharSequence mMessage;
    private Button mPositiveButton;
    private LinearLayout.LayoutParams mLayoutParams;
    private Button mNegativeButton;
    private boolean mHasShow = false;
    private int mBackgroundResId = -1;
    private Drawable mBackgroundDrawable;
    private View mMessageContentView;
    private int mMessageContentViewResId;
    private DialogInterface.OnDismissListener mOnDismissListener;
    private int pId = -1, nId = -1;
    private String pText, nText;
    View.OnClickListener pListener, nListener;
    public MaterialDialog(Context context) {
        this.mContext = context;
    }
    public void show() {
        if (!mHasShow) {
            mBuilder = new Builder();
        } else {
            mAlertDialog.show();
        }
        mHasShow = true;
    }
    public MaterialDialog setView(View view) {
        mView = view;
        if (mBuilder != null) {
            mBuilder.setView(view);
        }
        return this;
    }
    public MaterialDialog setContentView(View view) {
        mMessageContentView = view;
        mMessageContentViewResId = 0;
        if (mBuilder != null) {
            mBuilder.setContentView(mMessageContentView);
        }
        return this;
    }
    /**
     * Set a custom view resource to be the contents of the dialog.
     *
     * @param layoutResId resource ID to be inflated
     */
    public MaterialDialog setContentView(int layoutResId) {
        mMessageContentViewResId = layoutResId;
        mMessageContentView = null;
        if (mBuilder != null) {
            mBuilder.setContentView(layoutResId);
        }
        return this;
    }

    public void dismiss() {
        mAlertDialog.dismiss();
    }

    private int dip2px(float dpValue) {
        final float scale = mContext.getResources().getDisplayMetrics().density;
        return (int) (dpValue * scale + 0.5f);
    }
    private static boolean isLollipop() {
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP;
    }
    public MaterialDialog setTitle(int resId) {
        mTitleResId = resId;
        if (mBuilder != null) {
            mBuilder.setTitle(resId);
        }
        return this;
    }
    public MaterialDialog setTitle(CharSequence title) {
        mTitle = title;
        if (mBuilder != null) {
            mBuilder.setTitle(title);
        }
        return this;
    }
    public MaterialDialog setMessage(int resId) {
        mMessageResId = resId;
        if (mBuilder != null) {
            mBuilder.setMessage(resId);
        }
        return this;
    }
    public MaterialDialog setMessage(CharSequence message) {
        mMessage = message;
        if (mBuilder != null) {
            mBuilder.setMessage(message);
        }
        return this;
    }
    public MaterialDialog setPositiveButton(int resId, final View.OnClickListener listener) {
        this.pId = resId;
        this.pListener = listener;
        return this;
    }
    public Button getPositiveButton() {
        return mPositiveButton;
    }
    public Button getNegativeButton() {
        return mNegativeButton;
    }
    public MaterialDialog setPositiveButton(String text, final View.OnClickListener listener) {
        this.pText = text;
        this.pListener = listener;
        return this;
    }
    public MaterialDialog setNegativeButton(int resId, final View.OnClickListener listener) {
        this.nId = resId;
        this.nListener = listener;
        return this;
    }
    public MaterialDialog setNegativeButton(String text, final View.OnClickListener listener) {
        this.nText = text;
        this.nListener = listener;
        return this;
    }
    /**
     * Sets whether this dialog is canceled when touched outside the window's
     * bounds OR pressed the back key. If setting to true, the dialog is
     * set to be cancelable if not
     * already set.
     *
     * @param cancel Whether the dialog should be canceled when touched outside
     * the window OR pressed the back key.
     */
    public MaterialDialog setCanceledOnTouchOutside(boolean cancel) {
        this.mCancel = cancel;
        if (mBuilder != null) {
            mBuilder.setCanceledOnTouchOutside(mCancel);
        }
        return this;
    }
    public MaterialDialog setOnDismissListener(DialogInterface.OnDismissListener onDismissListener) {
        this.mOnDismissListener = onDismissListener;
        return this;
    }
    private class Builder{
        private TextView  mTitleView;
        private ViewGroup mMessageContentRoot;
        private TextView  mMessageView;
        private Window    mAlertDialogWindow;
        private Builder(){
            mAlertDialog = new AlertDialog.Builder(mContext).create();
            mAlertDialog.show();
            mAlertDialog.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE |
            WindowManager.LayoutParams.FLAG_ALT_FOCUSABLE_IM);
            mAlertDialog.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_MASK_STATE);
            mAlertDialogWindow = mAlertDialog.getWindow();
            mAlertDialogWindow.setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));

            if (mTitleResId != 0) {
                setTitle(mTitleResId);
            }

            if (mTitle != null) {
                setTitle(mTitle);
            }

            if (mTitle == null && mTitleResId == 0){
                mTitleView.setVisibility(View.GONE);
            }

            if (mMessageResId != 0){
                setMessage(mMessageResId);
            }
            if(mMessage != null){
              setMessage(mMessage);
            }
            if(pId != -1){
                mPositiveButton.setVisibility(View.VISIBLE);
                mPositiveButton.setText(pId);
                mPositiveButton.setOnClickListener(pListener);
                if (isLollipop()) {
                    mPositiveButton.setElevation(0);
                }
            }
            if (nId != -1) {
                mNegativeButton.setVisibility(View.VISIBLE);
                mNegativeButton.setText(nId);
                mNegativeButton.setOnClickListener(nListener);
                if (isLollipop()) {
                    mNegativeButton.setElevation(0);
                }
            }
            if (!isNullOrEmpty(pText)) {
                mPositiveButton.setVisibility(View.VISIBLE);
                mPositiveButton.setText(pText);
                mPositiveButton.setOnClickListener(pListener);
                if (isLollipop()) {
                    mPositiveButton.setElevation(0);
                }
            }
            if (!isNullOrEmpty(nText)) {
                mNegativeButton.setVisibility(View.VISIBLE);
                mNegativeButton.setText(nText);
                mNegativeButton.setOnClickListener(nListener);
                if (isLollipop()) {
                    mNegativeButton.setElevation(0);
                }
            }
            if (isNullOrEmpty(pText) && pId == -1) {
                mPositiveButton.setVisibility(View.GONE);
            }
            if (isNullOrEmpty(nText) && nId == -1) {
                mNegativeButton.setVisibility(View.GONE);
            }

            if (mMessageContentView != null) {
                this.setContentView(mMessageContentView);
            } else if (mMessageContentViewResId != 0) {
                this.setContentView(mMessageContentViewResId);
            }
            mAlertDialog.setCanceledOnTouchOutside(mCancel);
            mAlertDialog.setCancelable(mCancel);
            if (mOnDismissListener != null) {
                mAlertDialog.setOnDismissListener(mOnDismissListener);
            }
        }
        public void setTitle(int resId) {
            mTitleView.setText(resId);
        }
        public void setTitle(CharSequence title) {
            mTitleView.setText(title);
        }
        public void setMessage(int resId) {
            if (mMessageView != null) {
                mMessageView.setText(resId);
            }
        }
        public void setMessage(CharSequence message) {
            if (mMessageView != null) {
                mMessageView.setText(message);
            }
        }
        /**
         * set negative button
         *
         * @param text the name of button
         */
        public void setNegativeButton(String text, final View.OnClickListener listener) {
            Button button = new Button(mContext);
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                    LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
            button.setLayoutParams(params);
            button.setText(text);
            button.setTextColor(Color.argb(222, 0, 0, 0));
            button.setTextSize(14);
            button.setGravity(Gravity.CENTER);
            button.setPadding(0, 0, 0, dip2px(8));
            button.setOnClickListener(listener);
        }

        public void setView(View view) {
            ViewGroup.LayoutParams layoutParams = new ViewGroup.LayoutParams(
                    ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
            view.setLayoutParams(layoutParams);
            view.setOnFocusChangeListener(new View.OnFocusChangeListener() {
                @Override public void onFocusChange(View v, boolean hasFocus) {
                    mAlertDialogWindow.setSoftInputMode(
                            WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);
                    // show imm
                    InputMethodManager imm = (InputMethodManager) mContext.getSystemService(
                            Context.INPUT_METHOD_SERVICE);
                    imm.toggleSoftInput(InputMethodManager.SHOW_FORCED,
                            InputMethodManager.HIDE_IMPLICIT_ONLY);
                }
            });
            if (view instanceof ViewGroup) {
                ViewGroup viewGroup = (ViewGroup) view;
                for (int i = 0; i < viewGroup.getChildCount(); i++) {
                    if (viewGroup.getChildAt(i) instanceof EditText) {
                        EditText editText = (EditText) viewGroup.getChildAt(i);
                        editText.setFocusable(true);
                        editText.requestFocus();
                        editText.setFocusableInTouchMode(true);
                    }
                }
                for (int i = 0; i < viewGroup.getChildCount(); i++) {
                    if (viewGroup.getChildAt(i) instanceof AutoCompleteTextView) {
                        AutoCompleteTextView autoCompleteTextView = (AutoCompleteTextView) viewGroup
                                .getChildAt(i);
                        autoCompleteTextView.setFocusable(true);
                        autoCompleteTextView.requestFocus();
                        autoCompleteTextView.setFocusableInTouchMode(true);
                    }
                }
            }
        }


        public void setContentView(View contentView) {
            ViewGroup.LayoutParams layoutParams = new ViewGroup.LayoutParams(
                    ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
            contentView.setLayoutParams(layoutParams);
            if (contentView instanceof ListView) {
                setListViewHeightBasedOnChildren((ListView) contentView);
            }
        }


        /**
         * Set a custom view resource to be the contents of the dialog. The
         * resource will be inflated into a ScrollView.
         *
         * @param layoutResId resource ID to be inflated
         */
        public void setContentView(int layoutResId) {
            mMessageContentRoot.removeAllViews();
            // Not setting this to the other content view because user has defined their own
            // layout params, and we don't want to overwrite those.
            LayoutInflater.from(mMessageContentRoot.getContext())
                          .inflate(layoutResId, mMessageContentRoot);
        }




        public void setCanceledOnTouchOutside(boolean canceledOnTouchOutside) {
            mAlertDialog.setCanceledOnTouchOutside(canceledOnTouchOutside);
            mAlertDialog.setCancelable(canceledOnTouchOutside);
        }
    }


    private boolean isNullOrEmpty(String nText) {
        return nText == null || nText.isEmpty();
    }


    private void setListViewHeightBasedOnChildren(ListView listView) {
        ListAdapter listAdapter = listView.getAdapter();
        if (listAdapter == null) {
            // pre-condition
            return;
        }

        int totalHeight = 0;
        for (int i = 0; i < listAdapter.getCount(); i++) {
            View listItem = listAdapter.getView(i, null, listView);
            listItem.measure(0, 0);
            totalHeight += listItem.getMeasuredHeight();
        }

        ViewGroup.LayoutParams params = listView.getLayoutParams();
        params.height = totalHeight + (listView.getDividerHeight() * (listAdapter.getCount() - 1));
        listView.setLayoutParams(params);
    }
}

// My lib gardle : 
  compile 'com.github.afollestad.material-dialogs:core:0.8.5.6@aar'

Answer 1

AlertDialog alertDialog = new AlertDialog.Builder(context).create();

    // Setting Dialog Title
    alertDialog.setTitle(title);

    // Setting Dialog Message
    alertDialog.setMessage(message);

    if(status != null)
        // Setting alert dialog icon
        alertDialog.setIcon((status) ? R.drawable.success : R.drawable.fail);

    // Setting OK Button
    alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {

        }
    });

    // Showing Alert Message
    alertDialog.show();

试试这个......

在android studio中无法显示MaterialDialog？

1 个答案: